i quickly disassociated myself with TUMBLR once i felt the overwhelming effects of overexposing myself to the "arts", or in other words, visual stimulation. it had a negative impact on both my psyche and my own photography, thus i avoid it now at all costs. it's a great tool to signal to people how much of an amazing and unique person you are though.
most of my friends use it for porn though, which i don't understand given piratebay is littered with 720p and 1080p megapacks of every porn star imaginable, and tube8 and such is just a few keystrokes away. who the hell jerks off to images?