Why? It's a combination of not feeling like the name suits the child's personality, frustration with mispronunciation of the name and learning of negative associations with the name.
Let's look at how to combat these three common problems. The last one is the easiest: Do your research! Google, Google, Google your potential name. See who and what is out there that relates to your name in any way whatsoever. If you don't want to tell friends and family your name before baby actually comes, try visiting Parents.com's baby name group. Here, you can reveal your name to complete strangers and get honest, immediate feedback. Sometimes it's hard to think of the negative side of a name you really love, so other people are a great resource.
In terms of frustration with mispronunciation, it's best to really consider the spelling of your name before you make it official. If it's a common name, resist the impulse to make it "unique" by playing with the letters. Not only will your name be ripe for mispronunciation, but your child will always have to be spelling it out for people. If it's a less common name, the same rule applies: Go with the classic spelling. And if you've made up the name? Phonetics, please!
Hardest to conquer is the feeling that your name doesn't fit your baby's personality. Since you pick out the name when you barely know your kid, it's tough to find the perfect match. You can wait to make the final decision until baby is actually born, though, and at least you'll have some sense of who your child actually is. Another tactic is choosing a middle name with a very different feel than the first name -- that way, if things just don't seem right a few months in, you can always switch to the middle name.
What do you think? Have you experienced baby name regret? What did you do about it?