I don't know if many anyone makes a living from it, but the Palm platform appears to have some success with commercial software (or so it seems to me).

I've wondered if it was because various websites (such as www.palmgear.com) provide a ready-made marketplace. Plus, some prices are low enough to be very tempting (e.g. you might pay $6 for an memo pad replacement with encryption).

There is a lot of free software too, but I've found that I'm happy to pay for what I want.