This issue had came up when I was booking my last flight, and I was told you were not allowed to do this:

First Flight went from FLL to DCA with a stopever in EWR. Second flight was from DCA to EWR. Third flight was from EWR to Europe. For some unknown reason it was cheaper this way.

Now my question is, am I allowed to get off the plane in EWR and skip the other parts of the segments. Keep in mind this is only one half of a round trip ticket. The Eservice online person (very nasty BTW), said no. I never asked anyone at the normal Continental reservations line.