So @benbarry made some cool posters. Solid idea. Good job buddy. But seriously, everyone involved in this needs to contemplate the ridiculousness of these whiny teenaged first world problems. Print your posters. You can't copyright text on a page.
uh... what? Of course you can.
Granted, Fair Use may or may not come into play depending upon the length of the text being reused, but "text on a page" is exactly what copyright was invented for in the first place.
Sort of. Judging by a cursory glance at the USPTO indicates that there's no real hard-and-fast rule on just how much you can use, legally, before copyright kicks in. It's really something that has to be decided on a per-case basis:
http://www.copyright.gov/help/faq/faq-fairuse.html
In short: You can copyright text on a page. That much is obvious--that's why we have copyright, as you pointed out, but it doesn't just depend on length. It depends on presentation, typography, stylistic decisions, and so many other things that this particular situation is probably a legal gray area. That said, I very much doubt a judge would be willing to hear this, and I seriously doubt the designer would bother himself with pestering Facebook to take it to court.
Another argument worth considering is this: At what point does it become copyright and at what point does it become protected speech?