Net users used to say that "information wants to be free", but the new trend is for websites that will pay you to read them. Frequent surfers can collect cash in the form of ipoints or beenz the way frequent flyers collect air-miles, as website owners sign up for rewards schemes that encourage customers to keep coming back for more.

There's nothing new about loyalty or rewards schemes: millions of people used to save Green Shield Stamps, which involved sticking "trading stamps" in books. More recently, vendors have turned to new technologies, and card-based schemes from retailers like Boots, Tesco, and WH Smith have become popular.

It's no surprise to see the same ideas appearing online as more and more people start to shop the web.

Indeed, rewards schemes may prove even more important online, where automated search-bots make it easier to find the lowest price. On Saturday, a survey of 1,905 online shoppers conducted for the Associated Press by US-based internet research firm NFO Worldwide revealed that more than half (53%) of those surveyed said they would buy more if incentives were offered, and almost half (47%) said they would be more loyal to a site that gave rewards.

Only 15% said that rewards would not influence them to make more purchases.

"Ecentives" are certainly more convenient than off-line schemes. Aaron O'Sullivan, director of www.ipoints.co.uk, says "the really fun thing" about ipoints is that everything happens on the internet. "You join the scheme online, collect and check your points online, and spend them online. There's much more 'instant gratification' than when you have to write away for your points, get a brochure to spend them, and so on. We have people joining up and redeeming points at 3am!"

The lower overheads of electronic trading can also allow for larger rewards. O'Sullivan says: "We allocate about 7%-10% of the sales value for rewards, so it's a major, major jump on traditional schemes where it's 1%-2%. It means you get rewards three or four times faster. And it's not just about shopping. You can get points for visiting sites or for completing surveys, and you get points if you get your friends to sign up."

The ipoints scheme, which has signed up about 5,000 members in its first two months, will soon face competition from Zoom points, which will be launched "in about six weeks", according to Zoom chairman Robin Klein. The difference is that where ipoints are offered on disparate sites ranging from Amazon.co.uk to Screentrade, Zoom points will be limited to the Zoom.co.uk online shopping mall.

"It's a classical loyalty scheme," says Klein: "and a point is a penny: it's interchangeable with cash. It's a way to encourage and reward online shoppers, and an incentive to come back to Zoom."

Points won't be available on other websites, but they will be offered by brands owned by the Arcadia Group, Zoom's parent company, including Top Shop, Principles, Dorothy Perkins, and Burton Menswear. Other partners who trade through the mall - such as Amazon, Interflora, Jobsearch, and online auction house QXL - will also all be able to offer Zoom points. "And we hope they will. They'd be missing a real opportunity were they not to," says Klein.

Similar schemes have been running in the US for years, through companies like MyPoints.com, CyberGold, and Netcentives.

MyPoints.com's chief executive Steve Markowitz says the company's MyPoints and BonusMail loyalty programmes have attracted two million consumers in 18 months, and MyPoints are used by more than 250 clients including Disney and Dell. CyberGold says that more than a million members are collecting its points, which can be exchanged for cash, and it has just launched its own credit card. Netcentives has more than 350,000 members, and the merchants using its ClickRewards scheme include Gap, Yahoo! and OfficeMax.

But not all the American rewards schemes are open to users outside North America, and participating retailers may not be willing to grant points to non-US users, or redeem them. Even if they are, O'Sullivan argues that "people like to buy from companies in their own country. They probably know the brand names, they can get the product faster, and if something goes wrong, it's a lot easier to get your money back from a UK company."

What people don't like, of course, is having to cope with multiple schemes. They are already suffering from "plastic fatigue" caused by carrying too many bank cards, store cards, phone cards, membership cards and so on. Who wants online points that don't exist off-line? Why can't people collect, say, air miles online instead?

Judith Thorne, group marketing director at Air Miles Travel Promotions Ltd, says they can. "All of our clients will offer [air miles] online, and if you use your NatWest credit card to make online purchases, you get air miles on that," says Thorne. "So effectively air miles is not just an online currency, it's a retail currency as well. They're all going to have to do that, otherwise they won't survive. People don't want to have to collect one type of points online and another type when they shop at retail so we see [the internet] as a great opportunity to build on what we've already got."

But, like other rewards and loyalty schemes, air miles have limitations. You can collect air miles in dozens of countries but they're not interchangeable - frequent travellers have to carry different cards for different airlines - and they're not universal. "We have exclusive deals with NatWest and Sainsbury's and Shell and Vodaphone," says Thorne, "so we wouldn't work with Barclaycard or Tesco or BT and so on."

Does this mean there's a gap in the market for a universal currency for the web? Phil Letts - from the diary family - hopes so. Letts is chairman and chief executive of Beenz.com Inc, which launched beenz in March, and which is just about to begin a $10m direct marketing campaign through Lowe Direct.

"You can now earn beenz for doing the sort of things you do online in any case, you can save those beenz at the bank at Beenz.com, and you can spend them on a whole range of things," says Letts. "It's like money, but better. It's going to revolutionise the web, and it's a British invention!"

Traders can buy beenz from the bank and give them away to surfers who buy things, fill in forms or visit certain web pages. They can also ask visitors to pay in beenz for access to information that they don't want to give away free, but have no chance of charging real money for.

Since beenz is, in Letts' words, "a rewards system, not a loyalty play", there's nothing to stop competing companies from offering them. In fact, Letts sees beenz working in parallel with loyalty systems: "I think you'll find, before too long, we'll start exchanging beenz into some of those points schemes," he says.

"The beauty of beenz is that it has a real opportunity to become the universal rewards currency, and that's what the consumer wants: a standard."

Could beenz be used to pay for pornography? Letts barely misses a beat: "It's a free market," he says. "Porn sites are there to be stopped by parents or by governments, not by us."

Letts says the take-up of beenz is running ahead of expectations with about 150 sites offering beenz, 22 sites redeeming them, and more than 20,000 active account holders at the beenz bank. "Everyone thought we were a bit mad with our forecasting, but we've really over-achieved. We've got nearly 50 employees and a humming business and a great infrastructure so we can roll this thing out really fast now. You're going to start seeing some big names pretty soon, and we're going to start the consumer marketing this month. From September we'll start spending serious money, $1m a month."

Nor do Letts's ambitions stop with the web. "This thing is going to go off-line," he says, "and yes, we're doing some trials already with one of the leading smartcard players, and we'll be on WebTV and mobile phones by the end of the year. All of those things are in our plans, absolutely."

The ultimate fantasy is, of course, to have beenz quoted as a currency alongside US dollars, pounds sterling and yen. For Letts it would be like having the facility to print money, except that with an electronic currency, he won't even have to print it.