That, and also a blocking method that actually works. As it is now, all blocking does is make the person vanish from your dash (as far as I can tell), which does nothing to stop them from reading your tumblr and reblogging things. Tumblr is really terrible about privacy and security, unlike other popular blogging sites. When even Facebook has a more efficient blocking system, there’s a problem.
Blocking also doesn’t keep people from sending you asks.