Does anyone else ever get confused by how Tumblr is a combination of a blog host and a community?

I like the community, but the reason I started with Tumblr was to host my own blog.  I have friends who read it but don’t use Tumblr.  But there are people who follow me who aren’t my friend.  Who am I catering to?

Sometimes, I decide not to reblog something because it’s been reblogged so many times already and I don’t want to mess up people’s dashboards.  But then, I have friends that aren’t on Tumblr, who might not have seen it already.

There’s so much reblogging going on, sometimes with comments, that it’s like a closed-community forum, but these reblogs aren’t closed, so if I reblog something and comment on it, it’s open to the world.

This has always kind of bugged me and I’ve been here a year and I’m not really any closer to forming an opinion in it.