Geek has never been as chic: after the Gap cast the Foursquare founders to star in its winter campaign last year, Tumblr inventor David Karp is now modeling for the Japanese retailer.

It is a smart move for Uniqlo, given that Tumblr has had such runaway success in fashion that it is expected to take over from Facebook soon. Fashion bloggers have long embraced this latest outlet (see a directory of them here), and brands including Kate Spade, Oscar de la Renta, DKNY, and J.Crew have been following suit.

Tumblr is so popular in fashion circles due to its visually friendly nature and because it makes it easier to 're-blog' posts, which has resulted in fashion campaigns going viral more often than posts outside the field.

The video starring Karp, just released by Uniqlo, is likely to go viral too, not least because of its entrepreneurial advice and tips on how to run a successful Tumblr. Watch it at