Google announced today they had acquired satellite imaging company Keyhole (read the press release here)
This is very slick software that lets you zoom in on any part of the globe (even down to street level in some cases), lets you find businesses & facilities and lets you measure distances.

Even though it's a nice piece of software, I was a bit non-plussed as to why Google had bought it though, until I read this interesting post on the John Battelle Searchblog where he had a talk with the head man at Keyhole, John Hanke:

[...]Hanke showed an application, which he called geoblogging, which allows folks to fly around Keyhole's data and annotate various things they see. "They identify a spot, then talk about it, upload pictures they took there, whatever," Hanke told me. "That then becomes an icon, a point in the Keyhole database" that others can view and comment upon.

A super-detailed map of the globe that users can update themselves with comments, images etc?
After realising Keyhole could do that, the usefulness and potential of the software became more apparent. It will be very interesting to see where Google goes with it.

For examples of users adding to the Keyhole data, go to this site, it's a place where users have been uploading their own place marker files.
Look for the .kml attachments, clicking them in IE will send them automatically to Keyhole which will then zoom to the location.

More info:
Keyhole
Official Google Blog: Power of 2
Google Buys Satellite Map Firm Keyhole Corp.
Google Acquires Satellite Image Software Firm