The main concern is over privacy, according to civil libertarians. But that's a bunch of hooey.
Google uses AdSense, which is their program for delivering relevant ads to your email message. I think it is cool how it works.
GMail is email and chat all rolled into one. A long series of emails can be expanded where everything between all parties can be read and commented upon. Google's algorithm takes text from these emails and delivers links from advertisers about what was in the messages.
Talk about New York City. Boom. NYC links appear on the right. Talk about the NFL. NFL links appear. This is no conspiracy. They possibly wrote a simple Perl script to pull this off. I'm just mad that I didn't think of it first. Why else could they offer 1 gigabye of storage for nothing? That loss leader is delivering a profit to Google. No doubt about it.
I would advise anyone who has sensitive materials to transmit stick to their ISP's email. Don't use any free service.
