This has been a very common question. As near as I can tell, no one is viewing your private topics, but the number of views has to do w/ when the topics are accessed via email.
When someone sends you a private message, you're notified in email format too. So if that's opened it counts as a view.
BUT, the good advice I got was that if you want to be TRULY private, you'll take communicate via email.
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"People ask me what I do in winter when there's no baseball. I'll tell you what I do. I stare out the window and wait for spring." Rogers Hornsby, Hall of Famer