I was considering answering How prominent must terms of service be?; when I was struck by a thought: what is the point of website Terms and Conditions anyway?
Clearly, if they form a contract and they are properly brought to the attention of and agreed to by the user then they are binding (knowledge of and agreement by the provider could safely be assumed). However, one of the fundamental requirements of a contract is that both parties must provide valuable consideration. If the user is paying to access the service then this requirement is satisfied (e.g., a pay wall on a news site or a purchase agreement on an auction site). If they are not then they provide no consideration and there is therefore no contract.
For example, participation on this website is putatively subject to the agreement you can read by following the legal link below. How prominent must terms of service be? is the appropriate place to address whether the terms are prominent enough to constitute agreement (IMO it's arguable), so take it that they are. It is possible, that what we post is valuable consideration but I think that is worth a question on its own so I did Are the Q&A posted on Stack Exchange websites valuable consideration?, so take it that it isn't. In the absence of its users providing valuable consideration then there is no contract: What then is the point of the terms and conditions?
Clearly, such terms and conditions could be to draw the users' attention to legal obligations that exist as a matter or law without a contract (e.g., Copyright and other IP obligations). They could also be used to create rules that would allow users to be denied service, however, since anyone can be denied service for any reason so long as that reason is not unlawfully discriminatory, it seems pretty pointless.