"There's absolutely no way they'll make it search other people's email and show the results in your searches. It's going to pull from your email and your's alone."
Not on purpose, that is.
I'm done with Gmail. I'm tired of Google saving and archiving everything I do online. Based on your search patterns alone, Google knows where you are on any given day, who you bank with, what kind of medical issues you're searching for, problems you have, hobbies, interests, political views, etc.
And consider the data collection center built by the NSA in Utah (http://www.wired.com/threatlevel/2012/03/ff_nsadatacenter/) and I just don't want to do business with any internet company that stores information about me. There are plenty of companies out there that make it a point not to keep records.