In https://money.stackexchange.com/q/6842/2640 several people seem to assume that store-based credit cards are a bad idea.  What is the reason for that?  Is there something about them that I'm missing?

~~EDIT~~

A little background.

We just got a Target credit card.  We'd moved to a new area a couple years ago, and found that we were doing most of our shopping at the Target right around the corner from where we live.  The card is 5% off all in-store purchases except for gift cards.  Our other credit cards don't have better than 5% cash back.

We never carry a balance, so the rate of the card is a non-issue for us.