How can a class action lawsuit that you didn't know about affect you other than re: right to sue?

In the US, we have this concept of class action lawsuits where a bunch of people who have been wronged by someone (usually a faceless corporation), all get together and sue the crap out of the defendant. In real life, what it usually means is that a few people and some lawyers come up with the idea, formally define the “class” of people who are suing, and then take out nationwide ads (constructive knowledge?) to actually find these people so that they can file a claim for benefits, object to the suit or a proposed settlement, or opt out. If you don’t opt out, you are apparently bound by the court’s decision, even if you didn’t know that you were “part of the class”. To get out of it, you have to formally request to be excluded.

Now, my understanding is, is that if you do nothing (either because you can’t be bothered to respond or if you didn’t have actual knowledge of the proceedings because you didn’t read the right magazines or watch the right TV channels at the right time, and of course you don’t monitor every case filed in every jurisdiction) then you are normally legally precluded from filing your own lawsuit against the defendant later.

Is it possible to have other restrictions placed on you as a result?

E.g.:

Security Guard at WalMart: “I’m afraid you can’t come in. You’ll have to leave.”
Hapless Joe: “How come? What did I do?”
Security Guard: “There was a class action lawsuit earlier this year. The class was defined as all Black men between the ages of 20 and 30 who had shopped at WalMart in the past year, and the suit was over alleged discrimination regarding credit applications. The settlement was that every customer who applied for benefits by last month would receive ten dollars in exchange for staying away from WalMart for a year while all employees undergo sensitivity training.”
Hapless Joe: “I don’t care about that. I didn’t even know about it. I just want to buy some pants.”
Security Guard: “Please leave or I will call the cops and have you arrested for tresspassing and violating a restraining order”