Startups: Don't Host Your Blog on Tumblr
A mistake people seem to make is assuming Tumblr is a blogging platform akin to Wordpress.com, it isn't, it's a different beast entirely. The majority of Tumblr is the "community" of ~teenagers sharing pictures and videos and posts, Tumblr revolves around the dashboard not individual blogs. Sure you can host your company blog there, but do tumblr care about the uptime of that vs. the uptime of their dashboard?