Pokerpie: If you can't see it, then you're really not thinking clearly.
2ndLife has a large number of surrounding services that users have contributed. So not only is there plenty of typo traffic likely to happen, but a number of these also have affiliate programs that you could 301 to and make money in that manner.
With that said, the future of 2nd Life is definitely uncertain simply on the basis that it's not a game, so much as an actual world simulation. It has decent graphics and a physics engine of sorts, but there's no actual plot or objective. You merely recreate yourself inside it... and there are other systems that do manage to do this better, or other core features, such as 3D interactive chat, better.
IMVU boasts a similar ROI for its developers, even though it is significantly smaller in scope.