I'll make these two things clear before saying anything else.
1) I love it when other people recommend new series to me to watch. Otherwise I wouldn't have found half of my current fandoms at all.
2) I also like it when people talk about their interests and fandoms, even if I didn't belong to them. I myself am poor with starting conversations, so it's a relief to me really.
We are clear with these two things? Good. Now to the topic.
You could say that I use my tumblr account in three different ways. 1: I keep my own tumblr blog, of course, mostly reblogging things I like, 2: I follow what other people within my fandoms (Umineko, for example) do, and 3: I follow how my friends hype their own fandoms and what they do in general.
I have quite few tumblr blogs to follow, but my dashboard is always full of stuff.
What stuff, you ask? Well...
Sherlock.
Tom Hiddleston.
Doctor Who.
And other random stuff.
I'll discuss some of these fandoms separately some other time, but yeah. My dashboard is full of these guys. Not complaining or anything. It's just interesting to notice that these are probably one of the most active fandoms on tumblr. Not just my dashboard, EVERYWHERE on tumblr. (or even the whole Internet)
Another interesting thing is that spending time on tumblr is most likely one of the main reasons that have lead me to become almost a Sherlockian myself! And without even noticing it! Isn't that frightening?
...I mean, when you are reblogging some single sentence about Moriarty hacking the Olympics just because of Stayin' Alive, you SHOULD be alarmed :'D