Seems like a dick move. Would you even block your skype contacts if they message you?
I would especially block my friends if they do it. Because I specifically asked them not to talk to me over tumblr IM. I don’t want any involvement in tumblr IM. If my friends were to drag me into something I specifically asked them not to drag me into, what kind of friends would they be?
Like, I get that it’s usefull for some people but it’s not usefull for me. They can always talk to me over skype and if I can’t respond on skype, I sure as fuck won’t be able to respond on tumblr and whatever they have to say can wait.