There are no requirements for bringing your own books unless you are playing something odd (prestige class out of a non-wotc book, etc). The only requirement is that you must own the book to play the non-standard stuff. If I (or whoever is DM) is unclear about the class, rule, etc, we need to be able to make sure things are understood. Generally, if a player does not bring or buy a PHB, he/she can get by, but it is more aggravating than it is worth to be doing that. Most of our group are older professionals who work for our money and simply will not stand for some punk to break the spines or spill drinks on our books.
However, we do play at the FLGS. The owner has never made an issue over where you buy your books (so as not to alienate potential customers), but those of us that are the core of the group are mature and realize that we should at least respect the fact that the owner lets us game anytime we want for no charge or strings attached. He also is quite good to us (occasional free drinks, discounts, etc); therefore, as a group we really do not go for people bringing in a printed SRD, or a bootlegged book off of kazaa or whatever. I'm not going to raise issue on that stuff, but it is quite offensive and insulting to play for free at a very cool owner's game store and bring that crap in.