This Jon Udell article discusses how Google Maps provides a lot more than it first appears via his idea of "annotating the physical world." Cool stuff, BTW. I take exception, however, is his assertion that Microsoft could have done something similar years ago via TerraServer. He specifically calls out Google's use of open web technology and the lack of a Windows tax.

Well, I do disagree with his assertion a bit. I will try and break it down a bit so I don't ramble too much:

1. TerraServer never launched with near as much hype as Google Maps, and just as importantly, launched prior to the idea of distributed web apps really being practical. No web service standards to speak of or anyone even working on them (though XML RPC was probably in its early phases). Besides, TerraServer was about demonstrating SQL Server scalability, not being a distributed app platform
2. There is nothing preventing someone from extending TerraServer today. Web Service interfaces were fitted on at a later date. People have elected not to and mostly, I would argue, that TerraServer is a forgotten about entity in the developer space whereas Google Maps is all the rage right now
3. Windows Tax? Where? I don't see it. The TerraServer web services can be used from any platform to build a purely HTML interface. I will grant you that Google Maps provides more GUI goo to make building rich apps easier, and the graphics and such are much nicer, but that is more a benefit of being able to learn from all of the things that have happened since TerraServer launched.
4. Lastly, Microsoft is not doing what Google is doing, at least when TerraServer was built and in some specific scenarios, at least not right now.
5. Nobody in 1999 was pulling off this kind of stuff. Heck, most browswers couldn't pull off this kind of stuff. Of course, this all would be moot if Microsoft hadn't innovated back in the IE 5 timeframe by adding the XMLHTTP object to the browser, which was then copied by others and makes all of the Google magic possible.

I think the bigger, and more important question, is what would a solution from Microsoft look like if it elected to compete? A wickedly cool Avalon app (we are talking the future here) would do all of the eye candy stuff Maps is doing now and could be disconnected. It woudld be nice to pull some of that data for offline use since we are still a ways away from free, ubiquitious wireless.

Is Google Maps cool stuff? Absolutely. But to take a shot at Microsoft and TerraServer is a bit off.