One thing that I feel Tumblr does better than most social networks is discoverability. My experience is that as long as they are relevant/focused enough, tags

One thing that I feel Tumblr does better than most social networks is discoverability. My experience is that as long as they are relevant/focused enough, tags can actually work. One can discover good content and interesting people by following the relevant tag, and if you tag your post well, (at least some) people will see it (and like, reblog it, whatever). Because of that you can login without knowing a single other user on the service, and still quickly start to interact with like-minded people. Somehow, it's not true for all topics, though. Tech related tags are fairly empty.