Flew to PHL last month for a one night conference. Upon arriving at the airport for our return, we discovered that our flight back AC7917 had been cancelled. We were able to get shuffled off onto a USAIR flight leaving at 20:45 instead. No problem until we got to Security. All of us had to go through the extra routine:

Stand in the booth of presumed guilt.
Nod at our carryons being taken aside.
Stand on a ominous looking black mat.
Frisked by security staff sans shoes.
Told to sit in the chair of presumed guilt.
Told under no circumstances to touch our stuff until vetted.
Given our shoes back, given our stuff back and told to have a pleasant evening.

I assume this happened because we were all last minute travel changes.

THEN, we had to walk to our gate. If you know PHL, it was all the way from Terminal D to A West, a walk of about 16 miles. At least we had time for a nice dinner. The flight home was sparsely filled despite all the AC people trying to get home, so I had 3 seats to myself. Arriving at T3 instead of T1 was OK because it put me closer to the reduced rate lot with the Link train.

AND I had scored a spot next to the checkout booth the night before.

All in all, fun and games in the grand and glamorous world of business travel.