It may have been a weight problem you experienced, not an over sale of passenger seats, or a combination of both. I was already boarded on a flight from SXM to DC when they announced that they were overweight and started trying to get passengers to take comp to get off the plane. They kept trying and no one budged. They next said they would offload "cargo". The "cargo"? You guessed it, luggage. One of my bags included, even though we were FC and supposedly priority. Told in DC that "hmm, that was not SOP". Yeah, if your bags are to be off first when you land, I guess they were the easiest to grab and offload in this situation!