This is a terrible article.<p>The bald assertion that Tumblr is more successful than Posterous because it is faster is repeated about a half dozen times during the piece but no evidence is ever advanced to prove this point.<p>Without further data, at best, we're talking a correlation. I could similarly argue that dropping the 'e' in Tumblr is a 'big reason' Tumblr is more successful than Posterous (which, please note, contains an 'e'!).