The interesting thing is: There is no separate API required to use it. Because:
And labels act as schemas. Even though there is a lot of "control" - for e.g. can't specify a lot of words, there is enough power already. It is essentially a web-oriented database and it is going to make it easy for any application which fundamentally involves public data (such as looking for specific movies).
One question is: Would this database model result in Google making any inroads into enterprises over the time? For that matter, any other markets which are not driven by advertisements and end-consumers? For example, can small businesses hope to have applications hosted with this google database backend one day?
The answer seems to be "Yes, it will happen one day". The model opens up what I call "FolksFlows" - Workflows for general folks. What does this mean? Assume you want to set up a simple workflow. You have set of 10 sales people and you want to track sales on daily basis by these guys. Usual process is to get a guy to create a decent-sized application and worrying about things like how sales folks can update the data from field. But Google model will turn that upside down. We can now expect, with appropriate interfaces, a model where anyone can cookup a schema, use a wiki front end for UI, use google backend to store private data (this is tricky), and use Atom and other Web 2.0 approaches to provide interfaces. It can at most take about 2-3 hours by a common-sense oriented manager.
So the core of the problem is to use google database for private data. IMHO, it is actually easy part; I am sure Google will come out with a model for it as soon as Google base stabilizes. The second core of problem is: Ajaxi'fied Wiki front end that will use google base - and this is already in market by Dojo guys. And ISPs will follow suit as soon as someone targes one of the available open source wikis for this market (integrating, for e.g. Dojo toolkit for ajax-enabled widgets.)
Such apps can still use their own backend while using Google-provided standardized Schema. But Google Base will end up providing most easy way to integrate the app with other apps, and Integration is most difficult problem in these markets ...
So future is indeed exciting. Let us all hope FolksFlows will very soon become a reality!