"I don't think I could take that kind of rejection" - George McFly
Yes, there are some who might try to take your idea and run with it. But if you have the domain and the idea that goes with it and you can articulate it concisely again and again (and have a brief concise written expression of the idea), then you have the tools you need to work with. Think beyond Google. Who are you going to call after you get off the phone with them? Who are their competitors or wanna-be competitors? What interest would Yahoo! have? CBS? How about MSN and Microsoft? (they compete with everyone on everything). Can you put your domain up with some sort of affiliate program to make it look nice for when you start your conversations?
Remember that when you first express your idea, you only tell enough to get them interested and to invite you for longer discussions. Once you have them paying more attention, the better chance you have to get them to sign an NDA as well as establish a paper trail. Although building a case for any kind of infringement or hijacking of intellectual property is tenuous at best, it at least provides you some solice in the event that there is such a case. Most of all, doing things the "right way" will always tend to produce the best results. By the way, you want to protect yourself without blatantly communicating that you are trying to protect yourself.
Without continuing on to create an entire dissertation at this time, let me encourage you to pick up the phone (after you write down a little plan for yourself) and make the calls. Remember that the ball players who don't swing will never, never, never, ever hit a home run. Those who swing the most might strike out the most, but they also get the most hits.
Finally, my encouragement is meant as much for myself as anyone else. Two weeks ago I was ready to drop my price on LoanQuotes.com or try to unload it at auction. But after some study and thinking, I have begun to compose a list of a dozen or two banks and mortgage companies to contact. Then I also plan to talk to some big ad agencies about how this domain can be used in some strategic campaigns for their related clients. It can be hard work and I expect I will get lots of rejection. However, I understand that it is probably the best way to realize the highest value of the domain name.
All the best!