I have found a many great pics on Tumblr, as you have displayed here. That's the Good Side of Tumblr. The Bad Side is that I have also found and reported that many of our FF Members pictures on their as well. And once they reach that point they are like a Virus as they are shared and re-posted over and over again to other Tumblr Accounts.
Some of our best members like NanD, Greg & Alex, Pixel and Little Lo, Tha Cum Shot King & Shy Eyez, Exploder and Sinister, and Alison88 have had their pics spread across Tumblr many times (even with Water Marks). We lost Alison88 from posting anymore on FF due to some of the Idiots on this board who decided to post pics exclusive to this forum on those types of sites. Grrrrr