Why isn’t Marco.org built on Tumblr?

Marco Arment:

Writing your own blog platform is like roasting your own coffee: it’s impractical and you probably shouldn’t do it, but for people who really, truly care about it, it’s worthwhile to them for their own personal priorities that sound crazy to everyone else.

I really would like to do that to have full control over everything but I don’t have the know-how. Sure, I could learn it over time, but I’ve set my priorities elsewhere. So maybe I don’t care enough about my blogging CMS.