This post on “the official” Google Blog explains how, if you use Google Maps for Mobile and have the My Location feature enabled*, your phone sends anonymous bits of data (the data is not pegged to your account) back to Google describing how fast you’re moving. With that data (from yours and hundreds of other phones), Google can get a pretty good idea of how fast traffic is (or is not) moving to use in the “arterial traffic layer” of Google Maps.
I’m sure there are some privacy folks freaking out over this, but, hey, get over it. Google says they’re tracking the data “anonymously” and hey, if you can’t trust Google, who can you trust? (That was said with a sneer for those who may be irony-challenged.) Bottomline: If you don’t like it, opt out. Don’t use Google maps or don’t let them know where you are.
However, when you do, you’re “crowd-sourcing” traffic information by, frankly, doing nothing.
I’m sure there’s a term for this (or will be soon): ambient data? passive participation?
This is a great science fiction feature that allows me to feel like I’m contributing to a cause just by being stuck in traffic.
Fortunate for me, however, I live about three miles from the office and rarely have problems in that department.
*On the iPhone, it’s enabled if you answer “yes” when the phone asks if you want to share you location with the app.