Just over a year ago I was flying to the middle of US with some prototypes for an agriculural automation system in my checked luggage. Going through DTW and O'Hare to my final destination was fine and went without incident. On my way back, again with a checked luggage bag of protypes and tools, this little airport in northwest IA got evacauted and I was very forcibly questioned about why I was flying with these things.
What struck me was that the larger airports (DTW and O'Hare) couldn't have cared less, but this 5-gate airport in IA freaked out that somebody flying with three laptops in his carryon would also have a bag of tools and equipment.
The best part out of all of this was after everything was cleared up, I asked the head TSA person what I should do in the future to prevent getting searched and interrogated. His answer was "just open your bag and show the luggage agent what is in it." I still don't understand how that would help - I envision that the conversation would go something like "Hi, these look like pipe bombs. They aren't. You can trust me." and I would immediately be detained.
(Edited for formatting)