Yep. Ego.
Releasing an Android doesn't mean they'd have to give up on Meego or Symbian; it would just be a short term thing to get some mind share and press, just the way Samsung is using Android for now while Bada gets ready.
But nooooooo.......
Anyway, their REAL missed opportunity was not buying Palm. They could have had their own, closed source, proprietary, superior OS in WebOS that is ready to ship NOW, but they let it fall into H-P's hands. In fact buying Palm would have *also* given them instant entry into the N.A. market, along with relationships in Silicon Valley. But again, that ego thing.