I've never minded spoilers as much as some people, as I like having time to prepare for events. But I can seek them out on my own, thanks, so you needn't go out of your way to deliver them to me personally.
The lengths to which some will go to make sure that fans be spoiled to the book, to something they obviously care about, is mind-boggling. To actually take the time to ensure that a bunch of strangers enjoy something they do in their free time a little less because you, what, disapprove of it? Find it amusing? It's slightly sociopathic, in any case.
Anyway, there's a brave knight friending Potterists with the event and the page-number it occurs on as their username. I'm sure it isn't the height of their genius, either, so if being spoiled is something you care strongly about, now would be the moment to take a vacation from the Internet. It's a pity they can bully people out of using a service that many of us have paid to use, but what are you going to do.