Did you read through the FB Terms of Service back when you signed up?
When I last read through that (and which was admittedly a few years back), the ToS indicated that whatever you uploaded became available to FB in perpetuity, and for whatever purpose FB wanted to make of it.
Put another way, if you didn't pay for something, then there's a good change it's you that's what's being sold.
This comment is a complete non-sequitur response to the previous comment. It's completely true, but in no way addresses the points raised.
The Terms of Service are irrelevant to the idea of whether "it's the users that make Facebook". Put it this way: how useful would Facebook be if you were the only user?
The grandparent is talking as though Facebook has a legal obligation to do right by its users. This is not true, as far as I can tell. As hammock says, it can do whatever it wants with the stuff published, to the extent that it doesn't do something libelous with it.
Of course, it's not a good PR or long term business strategy to screw with lots of its users, but talking as though it must do things when it really doesn't have to is the issue that the parent is responding to.
I'm not sure which comment you're talking about, but falcolas' comment specifically says "...since there is no legal contract..." - the comment is clearly talking about a non-legal "need" for Facebook to treat it's users well. This has nothing to do with ToS.
If someone says Facebook "must" do something, it doesn't necessarily mean that they're implying a legal requirement. It is more likely that they're talking about something that, in the opinion of the commenter, is required to stay successful long term - regardless of the legalities.
When I last read through that (and which was admittedly a few years back), the ToS indicated that whatever you uploaded became available to FB in perpetuity, and for whatever purpose FB wanted to make of it.
Put another way, if you didn't pay for something, then there's a good change it's you that's what's being sold.