Hi, I've been running a blog on tumblr for the past year, never done any backlinking, it doesn't have a twitter/facebook or anything like that and not even any written articles, just pictures. I had a look at its PR today and it's PR3! This must be solely from backlinks on tumblr. Here is how I have got backlinks: -Reblogging other people's pictures and appearing in the "notes" on their page. -Other people reblogging my pictures and me appearing as the source. -Setting a click through link to my blog on all the pictures I post, so if people reblog them then they will be linking to me via the picture. -Changing the source to my URL. -I have 1,400 followers and don't know how much traffic I get, which just about sums up how accidental this was. So, from this it seems as if tumblr is a very good source of backlinks and I've got very good results accidentally so if you're using it from SEO on purpose, it could be a goldmine! What is everyone's opinion on this?