Originally Posted by
dvs7310
Actually for those that do collect miles, some airlines give the same online booking bonus for a one way as they do for a round trip, so if the one way is half of the round trip then you can get your bonus twice booking that way even on the same airline.
Some airlines don't give online bonuses at all for one-way trips (hello, US, can you hear me?).
A problem with buying a r/t is if you change the outbound flight you might have to reprice the whole r/t, thus potentially paying far more for the return.