I've been seeing this on a few Chicago blogs in the past week or so. I've been playing around with it and as a matter of fact I'm playing with it now. It's a great little toy. You can get a feel for a city you've never actually been so I'm liking it. If nothing else, you can have a look at a neighborhood in maybe any city that you're not very familiar with. Who knows you might find out that one area isn't as bad as the conception you've had in your head.
If you want to play with this program you go to Google Maps, then enter an address and the city and state and click on this button that says street view and you should be good to go.
This almost reminds me of when I could look for satelite images of a place. I did this a long time ago and I suppose I got bored with it.