While doing research for the followership interconnectedness post, I ran into the idea of a complex contagion. It means a pattern of behavior you have to see or read about more than once before you try it out or adopt it.
It reminded me of writing. I read more than five different posts to the tune of "write a blog!" before I started notebook blogging. Of the ones I remember, one was Zvi Mowshowitz and four were David R. MacIver (one, two, three, four). I suspect there were others before that though; I want to say this was a theme on Less Wrong for a while. Also, Steve Yegge apparently wrote something about this which I'm mostly but not entirely sure I didn't read. And less directly there's the Paul Graham essay on essays which I did read but isn't about blogging per se. This is too few things — there were definitely other things that I'm forgetting.
The first time I read it, it didn't stick. I had to read the same thing at least five times before it sunk in. That sounds like a complex contagion to me.