There is a potential for fraud from the user as well - taking your example:
The user can edit the html, print if off and say that /that/ was the TOS he agreed to.
I don't know if Google cache or the wayback archive are usable as evidence, that would be for a court to decide, but there is always the possibility that they didn't catch it, and the user can always say 'on X date, when I joined up, it said this and this (with the fake printout)', now the site has to prove otherwise.
In fact the user can just claim he never agreed to such a TOS, that no 'I have read and accepted the TOS' checkbox was displayed to him at any time.
That's why there is another clause that states "We reserve the right to modify these terms and conditions at any time and for any reason, with or without explicit notification to you."
This is why you always hear "be sure to get a good lawyer" when discussing legal issues. It's their job to protect you from liabilities. Sure there will always be cases where someone could present false evidence, but this is why we have a court system.
The user can edit the html, print if off and say that /that/ was the TOS he agreed to.
I don't know if Google cache or the wayback archive are usable as evidence, that would be for a court to decide, but there is always the possibility that they didn't catch it, and the user can always say 'on X date, when I joined up, it said this and this (with the fake printout)', now the site has to prove otherwise.
In fact the user can just claim he never agreed to such a TOS, that no 'I have read and accepted the TOS' checkbox was displayed to him at any time.