Try to create a Google account with, for example, a user name "alicesmith" and also a second Google account with a user name "alice.smith".
After you create the "alicesmith" account, if you try to create an "alice.smith" account Google displays a message: "alice.smith is not available."
The Google error message is a trivial bug because it can lead you to incorrectly conclude a third-party already has created the "alice.smith" account.
In fact, the "alicesmith" account owns the "alice.smith" account. Google ignores nonconsecutive dots in a user name, and should probably specify that detail on its "Create An Account" form.