Accounts are being terminated by tumblr. We don’t know how or why, but every time I tried to e-mail tumblr, they would tell me it was a glitch in the system. I highly doubt that right now it’s a glitch in the system, because it’s happening to a lot of people. The best thing I can currently tell people is to message firstname.lastname@example.org as soon as it happens. The faster you do it, the faster you’ll hopefully get your account back and the faster we might get answers!