The world might be facing war, the tech sector bumping along the bottom of a terrible slump, but these are heady days for one niche: Wi-Fi, or wireless internet access.

Last week's launch of the Centino chip from Intel, which plumbs Wi-Fi into Windows laptops, all but guaranteed that within a year most new laptops will have the ability to surf wirelessly built in (and yes, Apple users, I know: we've had this ability for years).

Moreover, laptops are becoming popular as replacements for bulky desktop computers. This, combined with the rapid rolling-out of new networks, means both the number of laptop users and the number of Wi-Fi enabled laptops will grow very quickly.

There is also a rash of new Wi-Fi "hotspots" appearing in the UK. Inspired Broadcast Networks - a new Wi-Fi provider - has just said it will create 3,000 new hotspots by the end of the year, mostly in upscale pubs. T-Mobile has also said it will expand its Starbucks network to 56 locations by the end of May. BT Openzone, which has the biggest existing network of hotspots, is also adding new locations.

But wait. This might be where the Wi-Fi equation begins to break down. At least two of these providers - T-Mobile and BT - are betting that we will be willing to pay lots to access the internet in coffee shops, hotel lobbies and airports. T-Mobile's UK charges, announced last week, suggest this is a premium service: £5.50 for an hour, £14 for two, £37 a month. BT charges even more: £6 an hour, £15 for 24-hours unlimited, £40 for 900 minutes a month.

The big question is: are all these new potential users going to stump up? Let's look at three reasons why they might not - or, at least, might not in the numbers T-Mobile and BT hope they will.

First, the prices are too high. When fixed line broadband internet access is seen as steep at £25 a month, paying up to £40 a month for Wi-Fi you're likely to use less will feel very expensive indeed. You could choose to buy access hour by hour, but at £6 a go you won't want to use this too often.

Second, you can't roam. A number of different Wi-Fi networks are springing up, and you will need either to buy access on a day-by-day basis - by far the most expensive option - or throw in your lot with one Wi-Fi provider. This will dramatically reduce your options for access, unless you can swallow your pride and stump up £5-6 an hour to use a rival network - while still paying a hefty monthly fee to the provider you can't use.

Third - and this is the one that gives the operators sleepless nights - there's the airconditioning scenario. Today, when you choose to go to a hotel or a restaurant, you're likely to take it for granted that it will be reasonably warm or cool: you expect there will be some form of air-conditioning. Once it was a benefit an owner could sell: today it is ubiquitous, and free.

The same is already happening with Wi-Fi, albeit on a small scale so far. Individual coffee shops and small chains of eateries are realising that they can tie sales of drinks and food to internet access. Wi-Fi is cheap to install and run, and it gives them an edge in their competitive main business. Notoriously flighty customers might choose to go regularly to a particular deli if they know there's fast internet access, even if they're bored with the sandwiches or prefer the coffee elsewhere.

Even McDonald's is getting in on the act. Last week the chain announced that 10 of its outlets in the US have Wi-Fi. If you're brave enough to use a laptop in one, you can now have Wi-Fi with fries.

All this is bad news for the subscription model being relied on by BT and T-Mobile. BT is in a stronger position, since it has managed to sign up places such as motorway service stations and airports where alternative Wi-Fi networks are unlikely to pop up.

Besides, BT stands to win even if we use someone else's hotspot: it's almost certainly a BT fixed line that provides the bandwidth anyway, and it doesn't matter to it if it is the user or the hotspot owner that pays the bill.

For T-Mobile, determined to "own" both the hotspots and the users, things are trickier. Already (albeit only in central London, for now) I have the choice of a paid-for T-Mobile hotspot in Starbucks, or a free hotspot in a deli nearby. Guess which one I'm choosing? (And the coffee is better too.)

Away from a few locations, such as airports and service stations, where we are already resigned to paying through the nose for anything, it's hard to see how today's hefty subscriptions are going to survive.

Paid-for Wi-Fi might find its niche in rural areas, where some enterprising souls are experimenting with ways to use it to bring high-speed internet access to areas which otherwise would be using dial-up.

But for those of us who live in urban areas, there is likely to be greater choice. And there will also be enough pubs and cafes willing to pay the nominal fees for bandwidth on the basis that we'll be happy to pay for high-margin coffee, buns and pints while we use the internet.

That is bad news for anyone hoping to sell this as some kind of premium service: the dreaded air-conditioning scenario has just arrived. For the people who sell laptops, bandwidth and coffee it's going to be business as usual. And for those of us who like coffee and the internet, it's great news: fast net access is becoming as free as the air we breathe.