Actually, I never used PSN until 2-3 years after I purchased my PS3 as I never really cared about trying it out. So I assume it's optional for me and also a lot of people who do not have Internet connectivity. I could go on with more examples, but you get my point.
I didn't realize you said OFW vs CFW, but if you're running OFW the only likely way you could be banned if you were using glitch-cheats and I haven't heard of anyone being banned from PSN using mishaps in games to their on-line advantage, but I think I've read in the past about a company banning people from certain game(s) for cheating (without CFW) - I could be wrong about this though (might of been PC games). There are other more crude reasons why one could be banned, but my name doesn't start with a G and end with a Y so I'm not going to get into those.
It's free in the context that you can sign up for free and use features that are free (services) such as online multiplayer or game updates but, once you purchase content then you've paid for that content and unless you've got their upgraded PSN+ you're still never paying for access. However, if you have paid to "lease" (read the contracts) digital content such as games, movies and music and also might have subscriptions to various "apps" like Netflix, HuluPlus and Vudu then currently if you're running CFW then you would have something to lose. If you're running OFW then you shouldn't be in any case worried about losing access to this content as Sony is solely banning people who have (1) modified consoles and (2) cheat in games with them.
I also do not think someone who has been banned that has paid for probably not-that-much stuff is going to try to bring Sony to court over these bans. We all know CFW users (well, 99.999999%) of them have illegal content on their hard drives and you can bet every cent you'll lose hiring a lawyer that Sony will mention this fact and have a nice list ready when you show up on day 1 - the same day your case is thrown out of court.
Back on the off-topic-topic > Electronic Contracts are a new thing, but do provide more of a certainty of your identity especially if you've purchased content using some sort of debit and/or credit card. Yes, there would be some exceptions like either your information was stolen by your child or in rare cases third parties, but those situations can be remedied. However, you're responsible for your children so you'd still be liable; as your roommate or some hacker then you'd have to press charges and/or sue. What I find more appalling to "pressing X" to agree is that when you purchase your PS3 it comes with an EULA printed in one of the Manual's that you are never given a chance to read before you purchase and furthermore you never sign anything stating your agree to this EULA you've never seen nor have access to until you open the system. That is way more messed up then when having to agree with on-line based systems. At least then you're given some sort of choice in the matter and also can read what you're being legally binded to before you sign for it!!!
You're entering in a binding contract without being able to read the contract beforehand!

