I'm not in a situation where I have to worry about this, but I've been wondering about it for some time.

Let's say you have a Tumblr, one that's not for professional or promotional purposes or anything. Just a place where you fangirl over stuff, and you have a fair amount of followers.
If you then published a book, would you mention in on your Tumblr?
A friend was wondering about this, and pointed out that it could get some interest in your book if any of your followers were interested, or if you had online friends who'd be potential buyers.
However, would it be considered unprofessional or a bad idea to have a personal/fandom Tumblr linked in some way to you as an author?