I have a Tumblr to which I never post; I just use it to save pretty images for my own reference, and stop in a few times a week or so. But I can see how it could become a bigger timesuck.

I am pretty sure that I couldn't use mine as just an image aggregator. I've been able to manage Facebook only by really not posting anything—I used it to announce my engagement and marriage and that was it—and not checking in daily, but I don't think I could do that with art. I'd run across really awesome things from the ancient world and odd historical articles and lots of pictures of the sea and I'd disappear.