OMG, Dave just ruined, like, 5 classics in one post!
In the case of HP, didn't we restrict the talk about that particular book to one thread, marked "SPOILERS!" etc. and people who hadn't read it yet didn't go there? I mean, come on--we can't very well police all the threads for talk about X book's plot for X number of days. ("Okay, moderators--until Nov. 1st, it is your job to keep all spoilers from Breaking Dawn off these boards!"). In some cases, we, the mods, may not want the book spoiled ourselves (I know I read the HP thread for someone else when that was going on . . .). And in other cases, we may not know a spoiler when we see one. I don't know Bella and Edward from . . . well, all those other characters I don't know.
Like AM says, I'd click at your own risk, and in the meantime let's try nicely to keep the spoiler chat to one discussion thread in book talk, marked "Breaking Dawn *Includes Spoilers*" or some such.