It's a common mistake to assume that just because something is written in legalese, that it is in any way legally enforcable. I had one site where part of the conditions of use was that users must wear a squirrel costume in order to use the site. It was there for years, and nobody ever noticed.
Mostly those documents are arse-covering for the site owner/creator...several pages of "if you do anything illegal using our kit then it's down to you". There may also be somewhat optimistic "expected codes of conduct" which are usually only read so that people can make sure that they've broken all of them and not missed any. Some -like El Reg's- are pretty reasonable (although having a "no trolling" rule and allowing a comment thread immediately afterwards was a bit on the masochistic side, if you ask me. Also quite meta; because asking El Reg commentards not to troll is a troll in itself. Some are power-wanks on the part of the site owners, and some attempt to modify user's behaviour which is about as successful as you'd expect. Legality (apart from the arse-covering) doesn't really come into it. Mostly it's simply a matter of "how much do I fear getting banned from this site" that dictates the amount of attention you need to pay to these things.
Either the Toronto chaps are very stupid indeed, or they have a clever marketing department who know that if the internet is asked to do something it will immediately do the opposite. Personally, I'm not going to link to Toronto2015.