Obasanjo's three reasons developers adopt new platforms : 1) to help them differentiate themselves, 2) to make things significantly simpler, or 3) to reach new markets. Plus he seems to add a fourth : better distribution.

For example, the platforms I've been excited about in the last couple of years : the Facebook / YASN-as-platform and Google Application Engine. The first is basically 3 (or maybe 4) while the attraction of GAE is mainly 2.