Are AppEngine's User IDs and Google's User IDs the same?

This page is a result of a question that was asked yesterday on StackOverflow.com. Should Google Appengine userId be treated as a secret? The question and the answers can be seen here. jmort253 pointed out that since google uses the User ID in the profile urls, it's ok for us to use them in public URLs. This made me wonder whether these IDs are actually the same? So I made this test page, and it turns out that they are not the same. Later, Kyle Finley pointed that the App Engine's User IDs are specific to the App Egnine App and hence they are not the same as your Goole ID. But here is the test page and you are welcome to test it yourself.

By the way, the App Engine's User ID should be treated as a secret and should not be used in public URLs. Here is the info from AppEngine's site:

Note: Every user has the same user ID for all App Engine applications. If your app uses the user ID in public data, such as by including it in a URL parameter, you should use a hash algorithm with a "salt" value added to obscure the ID. Exposing raw IDs could allow someone to associate a user's activity in one app with that in another, or get the user's email address by coercing the user to sign in to another app.
Read more here