… as opposed to just looking at their stuff as it goes by on your dashboard?
I ask because I think the only time I look at a tumblr page is when I follow a link from outside of tumblr.
I do run into tumblr themes when I follow a link to an individual post to comment via Disqus. (That’s the only sort of reply to her stuff that Simian Idiot reads.) But otherwise, I don’t run into themes very often.