I've only been messing around with Google Latitude for a few hours, but it looks interesting.

For those that remember Dodgeball, it's like a GPS-powered, next generation version of that. As opposed to you having to text in your location to Dodgeball which would then alert your friends, Google Latitude knows where you are without you having to do anything.

Here's how you would use it. 1) take out your mobile phone; 2) open Google Maps / Google Latitude; 3) see which friends are close to you via their thumbnail photos on the map; 4) im them if you want to get in touch (or just be happy with the sort of "ambient awareness" that comes with knowing where your friends are)

And because it's a Google product, and not some tiny start up, it's easier to pull in friends (from say, your gmail contact list), and use related features like Google Talk to interact with folks who might be close by with you.

I'm pretty open about my online identity, and will likely use this service. For the most part, I don't mind friends knowing where I am.

But I can see this being pretty scary for folks who are used to more privacy. Even though Google provides a number of privacy / opt in type features associated with Google Latitude, I bet even the mighty G will struggle to push such an invasive service to the mainstream.