Is Tumblr the new 4chan?

I'm not sure anyone who reads Startup Adventures has been paying attention to the sad story of Jessi Slaughter, 4chan's latest tween meme-toy, but you can read about it on KnowYourMeme here or ED here (NSFW). It's a fascinating story about the fluidity and power of the anonymous web, but a couple points in the articles particularly stuck out: From KnowYourMeme:

The effects of her videos being posted to /b/ and various Tumblr blogs brought out the best of Anonymous, who began trolling her with taunts of her being stupid and ugly. She replied with comebacks that had little effect on the trollers.

From Gawker:

Here's how the Internet's rage—funneled by Tumblr and 4Chan's infamous /b/ board—ended in this sad and ridiculous scene.

From ED:

She also seems to be an underage b& lurker or a total Know Your Meme n00b, due to her knowledge of several memes. She is the latest target of tumblr's and /b/'s ire.

Call me old or out of touch, but what the hell, Tumblr? 6 months ago, this would've been attributed to "4chan" or maybe "4chan and eBaumsWorld". In my world, Tumblr is the happy realm of new media hipsters -- artists, designers, entrepreneurs and urbanites posting the latest LCD Soundsystem track.

When did it suddenly become Encyclopedia Dramatica with more whitespace?

I get how it works -- Tumblr has taken serious VC money from some of the best consumer web investors on the east coast, and they need to continue to grow by orders of magnitude to justify the capital and achieve a proper venture exit. David Karp's a smart guy, but I have to believe that this kind of growth will constrain the company's ultimate value. There are a lot of reasons why Chris Poole has difficulty monetizing 4chan, but I don't think it's for stupidity or lack of trying. It's just hard to make money off Anon.

Perhaps this is still a really small segment of Tumblr's community. But given the natural virality of the platform, I would be seriously worried about these elements polluting the rest of the site. Don't get me wrong, I believe the anonymous web is generally a Good Thing. I'm just not sure it's a good business.