If scenesters from Brooklyn to San Francisco's Mission District want to have Tumblr cool-kid bragging rights, they'll have to pay, founder David Karp has decided. Why has Karp finally set his unflinching blue eyes on Tumblr's bottom line? His hosting bills must be starting to pinch. He'll begin peddling paid Tumblr Pro accounts later this year. Flickr, which just added video for its pro members only, charges $25 a year for extra storage, but Karp tell us he hasn't figure out how much to charge his users just yet. What will Tumblr "Pros" get for their money? Karp says he's got "more than 10 features in the queue" including a tool that allows readers to submit content, more customizable themes and special page layouts. Check out screenshots of the new features below, and then wonder with us: Are they enough for ego-tumbling millennials to agree to pay Karp's fee?

My own loyal Tumblr followers — well, 2 out of 45 — say the unnamed price is right. Union Square Ventures partner Fred Wilson agrees, with a caveat. "It makes a ton of sense," he told me. "They are still in the 'make the service great phase' though."

We agree. For all its impressive growth (9,394.1 percent, year over year), Tumblr can still only claim 510,000 visitors according to Compete.com. Flickr has 24.2 million.

Karp tells us he realizes free feature growth can't stop if he wants Tumblr's userbase to continuing growing so fast. Freeloading users will continue to get new features, too, he said. But they're going to be features that in turn help make Tumblr an ad-supported destination for the wider Web. We're guessing more pages like Tumblr's dashboard-like front page, except broken out into specific subject areas like "autos" and "women" so that ads can be more lucratively targeted.

New features that disproportionately raise Tumblr's hosting costs or require support, however, won't come for hipsters who don't give Karp their parents' credit-card number.

I'm pretty sure, however, that's there's one way to get out of paying fees for Karp's new features. Just a guess: Drive enough traffic to the site and Karp will be happy to comp your subscription and maybe more. Julia Allison new Web content company, for example, will be based on the Tumblr platform. And I bet she won't be paying.

Why? Paid subscriptions could probably pay Karp's bills. Fark.com founder Drew Curtis says TotalFark subscriptions bring in hundreds of thousands of dollars each year for his zany headlines site. But Karp's investors, including Union Square Ventures and Spark Capital, will pressure him to find a much larger revenue stream — something that gets its hands on all the money large advertisers aren't spending on the Web. Proctor & Gamble's annual advertising budget, at $1 billion, can buy a lot of airtime, but it can't get trust-funders who only watch The Office when it's embedded on the Web to change their detergent-purchasing habits.