Dive Deep into Creativity: Discover, Share, Inspire
One thing that I think Facebook and YouTube do better than Tumblr is giving people the ability to opt out of specific ads.
Especially being able to tell them that the reason you don't want to see that ad is because it's not relevant to you.
I don't mind a reasonable number of ads in exchange for a free service, but the ones here on Tumblr are so horrifically misaimed and there's no way to tell them that.