Google Base shows off its new API to developers who may want to hook into the service through applications. As Philipp Lenssen says, "Google Base is starting to get interesting... with the API, it's certainly looking much more like an online database than before." I would agree with that, but I don't think it will replace the need for a database any time soon.
The API allows applications to do everything from add and delete items, to searching through the Google Base inventory. For a good example querying, check out this demo created in PHP5.