To be fair, I get some real social justice news from the bloggers. It usually hits faster than if I were to look here or try to wade through various sites. Then it's just a matter of fact-checking that news ["Oh, so-and-so has said this about same-sex marriage? Lemme check..."] and then it's off to the races.
Also, with the way tumblr is set up you can make it like your own website with different links to their own contained pages, etc., So you have a place to point to and archive your experiences.