Tumblr isn’t a collective noun, it’s a website. If you’re trying to start a thing where we use the name of a website to refer to the community, that would be a MASS NOUN. pwnd.
My bad, the two are easily confused. So you realize that Tumblr can refer to the community and were just being obtuse on purpose to be a dick. Thanks for making the internet a better place.
Look, I can’t be the only person who’s tired of people making grand generalizations about how people on the internet need to learn their grammar. A lot of people don’t care about the differences between it’s/its, or there/their/they’re, and that’s fine. If you’re one of those people, don’t let anyone tell you that this makes your comments/ideas invalid, because it fucking doesn’t.
If, like me, you’ve worked on hard developing your written communications skills, it’s okay to be proud of them and show them off. But if you’re going to bitch about people using flawed grammar on Tumblr, you should make sure that your grammar is flawless, or expect people to catch you on it. If you’re a human being and your grammar isn’t flawless, then maybe you shouldn’t bitch about flawed grammar — or at least not get all pissy when people (like me) point out that you, too, can make mistakes (like confusing mass nouns with collective nouns).
A lot of English Grammar’s rules are arbitrary, so we should all be having fun with them! Happy New Year, kids!