Suppose I have what I think is a good idea for Google or Yahoo, how do I go about sending it to them. Google for example has an email address

but if you send to it you get a stock reply

"Thank you for your note. While we are not able to personally respond to all proposals, please be assured that we review every email we receive. If our proposal matches our current business and technology development needs, a Google representative will be in touch with you shortly. In the event that we do not identify an immediate match, we will keep your proposal on record for future consideration."

It seems from this that you have to send your idea upfront and open, but then how are you to protect the idea. What's to stop them simply saying "We were thinking along those lines anyway", or "keeping the proposal on record" until they release something similar?