Don't be surprised if some service providers come up with such promises some time in the future and can't keep up with them.
According to a recent decision by the Advertising Standards Authority, an operator (Vodafone in this case) can legitimately advertise their connection as being unlimited, then put in small print that fair usage applies with a set limit. In Vodafone's case, the limit was 1GB per month.
A case of over promising and under delivering is what is currently undermining users' confidence in the broadband sector. Many punters were promised 8MB broadband lines, very few of us actually reached that theoretical figure.
Bulldog is even offering an upgrade to 16MB and if my experience with e7even is anything to go by, you may be stuck with your current line after having paid an administrative fee.
You may then be told that your connection is too far for it to get any significant boost in connection. Tough luck for you; in effect, no one can prevent an ISP from coming forward and proposing a 100Mbps line using a ‘new and proprietary’ technology.
To be fair, broadband service providers are competing without any significant unique selling points as most are reselling packages. A few are selling below cost to grab market share - e7even.com was an example. We all know what happened next.