[wickedchicken]

Cost of keeping engineer/supplier secrecy [financial, intellectual, and morale cost], unable to use real people as beta testers, more difficult to involve outside research centers, encourages insular culture. "Oh, is that public now? I don't even know anymore."

In the case of something that has a developer culture around it (say, a chumby or something) you have a higher number of developers ready to go 'at the start' since they've had time to think about killer apps.

One could point at how early-stage multiplayer videogames are developed for a good counterexample.