i started a tumbler earlier this year which was fine when i had school holidays.
however the main disadvantage of tumblr is that if you can't post say, 5+ items a day, you needn't bother. this is difficult if you're posting original content - although i was posting found images, i spent on average at least ten minutes trawling bebo to find each one.
i stopped bothering after a couple of weeks.
anyway in the short time that i was maintaining it, i built up a pretty big picture collection which is still rotting there. god it's terrible. my interests are just too esoteric for this life.