Efreet can only grant wishes to non-genies. What's stopping them from enslaving some poor sap and then beating him until he wishes for the things they want him to wish for?
Nothing stops him until he goes to far and gets the attention of the kind of people who stop these things. Namely PCs I mean come on this is the stuff adventures are made of.
This has been used in a Pathfinder module, even.
Spoiler:
It's the main plan of the efreet villain in Legacy of Fire. Give one wish (with traditional options for twisting it) in exchange for two scripted wishes, all towards getting him what he wants.