Recently on UA I was carrying a carry-on suitcase, a laptop bag and prior to boarding I got my bose headphones out (with case) of my carry-on so as to not hold people up getting it out when I boarded. Anyway I was 'challenged' by the gate agent to put them back into the bag prior to moving past the gate. At first I thought she was joking (I've never been challenged before on any airline regarding this), then she stated that UA could be fined (I guess by the DOT) $10K if I didn't comply. I complied, however I don't know what the actual rules are...