“85% of Tumblr users post more than 20 times a month on average.”
Why is this? Creativity, yo!
“[T]he creativity is found in [Tumblr’s] most dedicated users. Photographers, designers and musicians can be followed, liked and ’ reblogged.’” …. [David] Karp [Tumblr’s founder] could evangelise on the force of creativity for hours.”
"(I feel so meta posting this in Tumblr :) ).