Dave Mason now skips msdb when he looks for deprecated feature usage:
In my previous post, I took a stab at monitoring deprecation events for SQL Server. It didn’t go so well. A deprecation event occurred more than 5,000 times in a very short period of time, and I got one email for every occurrence. Not good. Here’s what I kept seeing over and over:
USER_ID will be removed from a future version of SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use the feature. Use DATABASE_PRINCIPAL_ID instead.
It turns out the system stored proc msdb.dbo.sp_send_dbmail has a USER_ID() reference. I suspect an unrelated alert/email happened once, which executed sp_send_dbmail, which generated a DEPRECATION_FINAL_SUPPORT event, which ultimately led to another execution of sp_send_dbmail, which generated yet another DEPRECATION_FINAL_SUPPORT event, and round and round we go.
Click through for examples of deprecated features that various Microsoft products, including Reporting Services and Team Foundation Server, still use.