The big one that nobody's mentioned is that the airline will cancel any remaining flight segments on that ticket, without recourse unless you are very good at b

The big one that nobody's mentioned is that the airline will cancel any remaining flight segments on that ticket, without recourse unless you are very good at begging favors from customer service. So don't book a round trip SFO-NYC-BTV-NYC-SFO on one ticket and skip the NYC-BTV segment, because you won't be able to rejoin either for BTV-NYC or NYC-SFO.