A petition on the Downing Street website is asking the Prime Minister to stop ISPs advertising 'unlimited' broadband.

The problem is that many of these 'unlimited' deals are in fact subject to fair usage limits. One ISP noted for this approach is Pipex, who despite advertising a "unlimited" Pipex Max product, recently sent two letters to some users threatening to cut them off unless they curbed their usage.
Interestingly another ISP, Toucan, who are owned by the Pipex group have removed mentions of "unlimited" from their advertising.

The petition is open until 10th June and has over 1,500 signatures who agree with the statement "We the undersigned petition the Prime Minister to Insist that OFCOM and the ASA stop Broadband Providers advertising 'unlimited' services that are in fact limited in the small print or by un-defined fair use policies."

As Pipex are in the process of selling itself it maybe trying to offload some 'undesirable' users. The most likely bidder at the moment is BT, who have secured  regulatory approval to bid.