Droid Sans is a font for Android. How exactly is that a "common font"? I mean, there's a lot of Android users out there, but I would have to assume "common font" means fonts that are available on multiple different platforms.
Droid Sans not as common as the other fonts on the list. I threw it into the mix for a couple reasons. For one, the feedback from twitter suggested that Android might support fewer characters than other platforms. For another, I expected a lot of commonality between the other fonts, but Droid fonts were an independent effort so I thought there might not be as much overlap.
"Common font" here probably means those fonts that your content is likely to be displayed in. Some Android applications will use Droid Sans, so it counts.
