This is true of bloggers, of Twitter users, of Flickr users… everywhere you look, if someone is using Firefox, they’re way more likely to be using other power tools online. The reasoning: In order to use Firefox, you need to be confident enough to download and use a browser that wasn’t the default when you first turned on your computer.

That’s an empowering thing to do. It isolates you as a different kind of web user.
Seth Godin on Firefox Users