well, for a contract some sort of exchange has to have taken place. The website has given usage of the site, but the user has not given them payment. So yes, they don't have a breach of contract if they are refused access to the site - but wait! Some intrepid person could waste a lot of money arguing that all the personal data the site collected was of value and therefore an exchange happened that meant they could not just cancel access to the site, unless of course they also scrubbed that data etc. etc.
