The good folks at TSA sometimes drop the ball as it were. I walked through the gate with my Spyderco Native and didn't hide or conceal it. I simply forgot about taking it out of my pocket prior and dropped it into the tray with everything else. The guards didn't even look: they were too busy discussing which one of them knew the most words to a rap tune.
I've had no issues packing items in my checked luggage, but I make sure to keep the valuable things, like my multitools or knives, layered in. What I mean by that is that I put the knife inside something else... like a portfolio or something, and then THAT goes inside a pocket or pouch that is zipped, buttoned or snapped... and then THAT is packed under everything and strapped in or otherwise secured. The key (in my warped mind) is to make it take SO long for someone to steal it that the fear of being caught overwhelms the perceived value of the item for the thief.
Just my $.02 oworth.