Microsoft used to issue press releases about how they were going to build a product in category X, killing all venture capital in category X. In many cases they never built a product in category X or if they did it sucked. But they were able to cut off the air supply.

Apple and Google don't do that.

This may sound trivial, but it is huge- it means you have a couple years to build traction and a chance of getting acquired by Apple or Google (as say, SIRI was).