Microblogging site Tumblr is reportedly poised to receive a big round of funding that would send its valuation to about $800 million.

Shaky economy or not, some investors are still steadily placing bets on tech startups with cool functionality but no clear revenue stream, and microblogging site Tumblr appears to be the latest example.
The New York-based Web platform is poised to raise $75 million to $100 million in venture capital, an investment that would place the company’s value at $800 million, sources told the Wall Street Journal today.
Tumblr’s lack of revenue—it doesn’t charge most users to create a blog— kept some major Silicon Valley venture firms from signing onto funding, but Greylock Partners, an investor in Facebook Inc. and Groupon—is among those planning to plunk down big bucks on the company, based upon its sizable user base, the sources said.
The new round would add to the $30 million the company received in December from Sequoia Capital, Spark Capital and Union Square Ventures in an investment that valued the company at $120 million. Neither Greylock nor Tumblr would confirm the fresh investment, the Journal notes.
David Karp, then a 20-year-old high school dropout, launched the site as a way to make blogging easier back in 2007. Now CEO of the company, whose name stems from tumble log or mixed media blog, Karp has been earning business awards, such as Best Young Entrepreneurs 2009 from Bloomberg Businessweek, and rave reviews from tech writers for its ability to let bloggers quickly add photos, quotes, links, music and video.
Karp spoke about the company’s quick growth at the recent TechCrunch Disrupt Conference in May, explaining that the exponential growth in users and the size of the staff (it went from about five to reportedly 45 now) kind of knocked the young company for a loop at first.
Tumblr boasts 13.4 million unique U.S. visitors, as of July 2011, up from 6.7 million users in December, according to comScore statistics cited by the Journal. That means it lags behind rivals such as WordPress, which has 44 million users and Blogger, which is owned by Google and boasts 64 million users. But it bests both of those competitors by large margins when it comes to another key metric: U.S. page views, for which it had 3.8 billion in July versus 282 million page views for WordPress and 718 million page views for Blogger.
Why so many clicks versus uniques? Tumblr is very popular in the fashion community, with about 20 percent of the company’s 27 million blogs related to fashion, making heavy uses of images. Maybe fashion types and investors are on the same page: if something looks good, it counts.