The LA Times published a piece on Tumblr earlier in the year that includes pieces of their projected revenue strategy -http://latimesblogs.latimes.com/technolog

The LA Times published a piece on Tumblr earlier in the year that includes pieces of their projected revenue strategy -http://latimesblogs.latimes.com/technology/2010/04/tumblr-ads.html http://latimesblogs.latimes.com/technology/2010/04/tumblr-ad.... At the moment, it looks like themes are the central piece in their monetization plan.