Some psycologist/economist did a study and it turns out that people buy gifts poorly. In other words, fully 20% of the gift giving dollar is spent badly.. on things other people don't want, and is therefore wasted. Another study showed that the better someone knows someone else the more likely they were to choose something the other person didn't want or didn't like!
Most of the poor giving is people buying things they themselves wouldn't mind receiving, forgettting, in the frenzy of the thing, that the recipient might not feel the same way.
In other words... don't take it personally, they're only human.
That said, I've become a master of the re-gift myself. In a good year I can get a gift in and out the door in the same year with no storage involved. There are some people who think this is a Bad Thing. I look upon it as getting the gift where it was meant to go if only everyone were as wise about these things as I am... ;-)
I also, by the way, make sure that anything I'm unsure about... you know, those "obligatory client gifts" or the little "housewarming thanks for the party gifts" are wrapped in clear celophane with fancy bows. A gift that just begs to be re-gifted if I haven't nailed it correctly. I've got one gift like that that I think has changed hands 4 times now and has become a bit of a local joke.
Doesn't hurt my feelings in the slightest. All part of the holiday fun.