There was a stretch of time when my laptop bag would get searched about 1 out of every 5 or 6 times I traveled. During this period I would occasionally later notice that items were missing (things like a nice Montblanc pen or similar).

In self defense I started locking the zippers together before placing my bag on the in-feed belt. Oddly enough, in the 2 years since I started that practice my bag has not had a single hand inspection.

It seems to me that TSA screening practices are just as predictable as the behavior of pickpockets.