I can't see how one would ponder either of these things before the much simpler 'is this a good platform on which to distribute my research on a highly sensitive topic' and then somehow arrive at 'yes, yes Tumblr is'.
though I agree, tumblr isn't exactly my first thought. :P
http://www.belfercenter.org/person/christopher-anzalone
Maybe at an academic institution would be best. Tumblr seems like an obviously iffy choice with a high risk of the work being misidentified/misinterpreted and then tossed out.