I'm betting, Tumblr is doing it's best to seem as profitable as it can be considering the possible Verzion buy. Tumblr want to make sure they look as good as they can do they don't get axed by Verizon if the deal goes through.
My bigger concern is Verizon's buyout causing a change of TOS in Tumblr. Tumblr had the same issue when Yahoo bought them. Yahoo tried to clamp down on the adult material but for the most part if failed. Will Verizon do the same? Tumblr is one of the few mainstream places where adult material can be posted without TOS violations.