This has also happend to me, except the DL employees at Logan Airport said it was a computer "glitch" that moved me from my exit row isle to a middle seat towards the back on a close to oversold flight... Gosh I was pissed, and nobody could fix it. Interesting to note that it appeared to be some non-revs that ended up in our seats... An older couple that boarded right before the boarding door was closed. Interesting that DL would not change my seat back... Hmmm....