So far we’re incapable of recognizing what all of these communities mean in the grand scheme of things. Twitter and Tumblr are big tent communities with so many little pockets of fandom and culture, so when users see something that they perceive as invading their space (ex. The Heritage Foundation tumblr, Bieber fangirls, this transethnic junk that’s been getting blasted lately), the reaction is to shun this stuff as publicly as possible to push it away to the furthest edges of the internet.
Before Twitter and Tumblr, you could practice your fandom in the privacy of a discussion forum. You could say something stupid and maybe 100 people will bust your shit about it. Now you say something stupid and 10,000 people bust your shit about it, and then they start judging an entire generation over it. All of what you love or hate can be distilled with a tiny search box. All it takes is one person to pick this stuff from the periphery and plant it right in your eyes.
FWIW, that Bieber tweet WAS funny, but there’s no broader implications for society that can be derived from it. If she was a teen in my day, she’d be covered in N’Sync gear and writing love notes to Joey Fatone all day. Instead she’s tweeting and according to TDW and Matt Stopera of Buzzfeed this is the end of the world.