It looks like Google Maps is finding it's way into another emerging urban net-tool. It's called FoundCity. Here is the description from their website:
FoundCity is a collective mapping tool. It allows everyone in a city to map the interesting things they discover throughout the day to a dynamic online map, where they can then compare their points of interest with other people's points. In doing so they both share what they like about the city with others, and discover what other people find fascinating about the city. It is an open-ended, continually evolving tour guide to the city.
It uses "tags" similar to Flickr.com. So by clicking on the tag "cool.building" you'll end up at a map plotting for you describing a slanted wall w/ circle windows at 346 w and 17th st. The site goes on to say that it is just available in Manhattan for the moment.