I beleive it's an imigration thing
Eddy said:
It's probably a USA thing.
I beleive it's an imigration issue. The country you are arriving in is suppose to ask you to show your return ticket upon entry. In most cases they never do,(I have never been asked in the DR) Requirements vary, depending where you're leaving from, I beleive that Canadian laws require you to have a return upon departure, and in the states, although it is not required, most airlines(AA for sure) will try and tell you, you have to have a return, in fact it is not true. You can buy your return in the DR.
I have also noticed, and from others postings that where the ticket originates from seems to make a difference. While an AA agent in Miami might give you a hard time, one in New York might not.
Worst note senario would be that imigration would make you puchase a return on your entry.