O2 sensors are right on the cusp of being just as reliable in a 2-stroke environment as they are in 4-strokes.
Some are capable of extended closed loop operation in 2-strokes with the use of a simple air/oil separator.
Most EFI setups on quads and dirtbikes are open loop anyway, so not having an O2 sensor isn't a deal breaker.

The fact that there's several 2-strokes already retrofitted with EFI systems, like the dirtbike video in Starpuss' thread, just proves that EFI can be successful on a 2-stroke (a 500cc single to boot).
I just want to see an LT fuel injected, for better or worse.
I think it would be a great learning experience, and an alternative to the same old crap that we have to choose from right now.