Is Tumblr the new Facebook or the new MySpace?

Tumblr, the combination blogging platform and social network, has been growing rapidly of late — so rapidly that it is now racking up about 8.4 billion pageviews a month, according to a blog post from president John Maloney. One of the big drivers for this growth appears to be teenagers, who are using the site as a kind of combination of Facebook and Twitter, to share photos and other Internet “memes.” But will Tumblr ever figure out how to make money from this massive user base? Other social networks have grown just as large and still failed.

Hitting the 8 billion pageviews mark would be a milestone for any Internet company, since that puts Tumblr in the top 25 websites in the world, according to Quantcast. By comparison, the popular classified site Craigslist gets more than 20 billion pageviews a month. And Tumblr’s growth continues to accelerate: according to founder and CEO David Karp, the network posted more than 400 million pageviews in a single day last week, which amounts to about 5,000 every second. If that kind of pace continues, it would put the company at around 12 billion pageviews a month.

Of course, pageviews alone are not a great benchmark for websites, since they can be inflated in any number of ways. When it comes to actual visits by unique individuals (as measured by Quantcast’s tracking), Tumblr is seeing about 355 million a month. By comparison, Facebook gets almost that many every day.

In other words, Tumblr isn’t going to overtake Facebook any time soon. But the pace of its expansion is still incredible: the site has grown by more than 50 percent in the last couple of months alone, and its traffic is now double what it was just six months ago — and that’s despite a massive outage six months ago that had some wondering whether the network would be able to recover. The outage doesn’t seem to have even caused a blip in usage.

Tumblr President Maloney says that one of the big drivers behind the network’s rise is teenagers, and that can be seen in the Quantcast data as well. About 16 percent of the site’s users in the U.S. are between 13 and 17 years old, and more than half are between 13 and 34 years of age. My own anecdotal experience confirms this: for my two daughters, both of whom are in that key 13-to-17 age group, Tumblr has almost overtaken Facebook in terms of the role it plays in their online lives. My 17-year-old spends hours sharing photos and Internet memes with her friends, and “Tumbling” has become a verb in our house.

As I’ve written before, Tumblr seems to have found a sweet spot between traditional blogging platforms like WordPress (please see the disclosure below) and social networks or “micro-blogging” platforms like Facebook and Twitter. While it’s relatively easy to set up a WordPress blog, creating and using a Tumblr blog makes that process seem complex by comparison. But even more important than that is the Twitter-style “following” that the site allows, and the fact that content can be “reblogged” on your own site with a single click — both of which can drive content on the network to “viral” levels in the blink of an eye.

This is why so many media outlets have begun experimenting with Tumblr blogs, including the New York Times (s nyt) (and GigaOM, which has started a blog we use to share interesting items we come across during the day). Newspapers like the National Post have seen incredible traffic from a single post that got reblogged and commented on thousands of times, and media advisor Steve Rubel recently nuked his WordPress blogs and moved everything to Tumblr to take advantage of the real-time nature of the platform.

All of this growth is wonderful for Tumblr, which was started by David Karp four years ago, when he was just 20 years old — but the big unanswered question is whether the network can actually bring in revenue to match that growth. Everyone wants to be the next Facebook, which many early observers doubted would ever find a way to make money and now brings in revenues estimated at $2 billion. But MySpace (s nws) also grew to massive levels, with more than 76 million users at its peak, and was bought by News Corp. for $580 million, only to rapidly decline after it failed to figure out how to make money.

So far, Tumblr has experimented with selling custom themes and other features, but it hasn’t shown any signs of being able to turn on the revenue tap in the way Facebook has — in fact, not that long ago David Karp was saying he had no interest in putting ads on the network. With $40 million in funding, he may have the luxury of not having to worry about funding for awhile, but Tumblr will have to answer that question at some point or risk becoming the next former red-hot growth story.

Disclosure: Automattic, the maker of, is backed by True Ventures, a venture capital firm that is an investor in the parent company of this blog, Giga Omni Media. Om Malik, founder of Giga Omni Media, is also a venture partner at True.

Post and thumbnail photos courtesy of Flickr user Gabrie Coletti