Rhodri Marsden: Why is so much broadband sold as 'unlimited' when it isn't?

If you're lucky enough to be told that you have "unlimited" access to something, you'd be forgiven for assuming that you won't get a slapped wrist when you help yourself to as much as you like. Take the gluttonous concept of the "all you can eat" buffet: the restaurant staff might roll their eyes if you return to load up your plate for the sixth time, but there's not a lot that they can do about it. Because that's what the sign promised on the way in.

Internet service providers, however, seem to have a different understanding of the word "unlimited"; for many years now, they've used it to mean "unlimited, right up to the point at which we decide to limit it". Or, in other words, "limited".

According to recent research from uSwitch.com, 86 per cent of UK broadband customers – that's more than 14 million people – still haven't got their heads around this rather self-contradictory concept. And who could blame them? Without wishing to give undeserved proper dues to Rupert Murdoch, Sky's Broadband Max service is currently the only broadband deal in the UK that's genuinely unlimited. All the rest, without exception and despite advertising claims, are subject to fair-use policies.

But the level at which this kicks in is rarely specified; more often you're advised, in tiny print on page 8 of a contractual agreement you probably haven't bothered reading, that you must stop short of "excessive" or "heavy" use – whatever that might be. Essentially, you don't know you've breached the terms of your contract until you receive a stern warning for having breached it.

Now that an EU directive has put paid to British theatrical promoters using quotations such as "More!" on their posters when the original review read "I beg you, no more", perhaps the mundane but equally misleading descriptions of gigabyte limits will be up next for scrutiny. It's fair enough that ISPs should be able to implement measures to stop their service being abused – particularly now that data-intensive applications such as iPlayer or BitTorrent are becoming more popular – but crowing loudly that they offer a totally unrestricted service isn't fair.

And worse, it's happening with the implicit support of the Advertising Standards Authority, who aren't cracking down anywhere near as hard on ISPs as the ISPs are on their data-hungry customers.

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