I can understand that. I have previously abandoned a series after reaching a point where I didn't like what was going on. (In one case I later found out that wasn't actually the last book, so I might go back to it sometime.)

I should probably have clarified that I'm not actually planning to spoil anybody. :)

But I do think that most people who spoil out of malice wouldn't have thought about it if there had been less of a production made. If accidentally finding something out early were treated as the nuisance it usually is rather than a total destruction, the reaction wouldn't be worth the trouble. If the focus were more on "Some people like to be surprised, so even though you're eager to discuss the story, please try to keep it down in public" rather than the accusatory "I can't understand why anybody would want to ruin the experience for readers," I think fewer people would feel contrary about it. Maybe this has been successful in terms of marketing, and maybe JKR honestly thinks that it makes no difference to marketing and is an important way to protect her readers, but I think some of her efforts and the publishers' have been a little counterproductive.

On the other hand, where less fuss is made, apparently you have headlines blaring Captain America's death before the issue comes out, with no thought that it might annoy anybody who matters. So maybe I'm wrong.