the stores are so flooded with people right after the holidays, most stores are quite lax when it comes to returning things for cash unless you spent a lot of money on the gift, in which case you've probably thought about it enough that they won't want to return it.
plus, i've found the number of people that take offense to the act (those that think you're showing off the fact you spent x amount of money) still outnumber the practical among us who realize they're just taking into account that there might be something out there you want more.