Tens (or possibly hundreds) of thousands of people use Jekyll now. It's interesting to note that Jekyll started out as a "brain fart" as well. Just one amongst hundreds of blog engines. I wrote it because I was dissatisfied with everything on the market, and I thought I could do something different and better, to serve my own needs. I open sourced it, because I thought others might get a kick out of it.
I'd wager that most of the great things we use today started as nearly ephemeral emanations from someone's mind, often late at night, or helped along by a snifter of brandy. The funny thing is, if you never try out your crazy ideas, you'll never know which ones might have changed the world.