Like many a Web 2.0 entrepreneur, David Karp hopes his product will be used by millions of people one day. But unlike other ambitious founders, the 21-year-old founder of micro-blogging tool maker Tumblr Inc. isn't planning an expensive, massive marketing blitz to grow the user base from today's 170,000 to one million people by year's end. Rather, Karp is focusing intently on satisfying his core audience of creative individuals and counting on them to spread the word to the masses -- much as Apple Co. evangelized its products.

In the meantime, he's carefully spending the modest $$775,000 he's raised from venture capitalists (such as Spark Capital and Union Square Ventures) and angel investors (including Betaworks founder John Borthwick, the Argentine-Spanish entrepreneur Martin Varsavsky and Jakob Lodwick, the founder of Vimeo who was recently ousted by its backer, IAC/InterActiveCorp). Besides Karp, Tumblr has only one other full-time employee, a programmer named Marco Arment. There is also a part-time community relations manager and a part-time designer.

Karp and I had lunch Thursday at the Flatiron District's lovely Indian restaurant Tabla, where he outlined his strategy. (If you don't know what the Tumblr blog tool does, check out the results of using it in Karp's blog.)

Tech Confidential: Critics say that Tumblr is designed by techies for techies. How will you make it mainstream?

David Karp: We certainly launched Tumblr to the first-adopter crowd, but our focus from the beginning has been building a mainstream product and introducing this form -- tumblelogging --  to millions.

TC: Without a big marketing campaign, how do you plan to reach a big audience?

Karp: By going out of our way to keep our users really happy. Forty percent of our traffic comes from referrals. If we focus on the people who really love Tumblr--the artists, musicians and other creative people who are doing the most brilliant things with it--and we help them to take what they're doing to the next level, then they will inspire and magnetize other people to Tumblr.

TC:  Why do you think the strategy will work?

Karp: Apple gained a tremendous amount of mainstream acceptance by magnetizing people to the "coolness" of their products. They drove that by paying a huge amount of attention to the coolest people doing the coolest things with their products. Everyone else saw what creative people were doing Apple's products, and they got jealous. They had to have one for themselves. We hope to do the same with Tumblr. -- Mary Kathleen Flynn

See Oct. 2007 post on Tumblr funding from Tech Confidential

See Jan. 4 post on Jakob Lodwick from Tech Confidential

See Nov. 5 2007 post on Martin Varsavsky from Tech Confidential

See Nov. 1, 2007, post on David Karp from Tech Confidential

For more on Tumblr and Karp, see Jan. 15 profile from The New York Observer, Oct. 2007 blog post from Fred Wilson and David Karp's Tumblr blog