These can be fairly substantial for those that start and cancel a bunch of cards just to get the points/miles, whatevers. THe number of inquiries goes up, and this can have a large impact on a good score. Maybe it doesn't matter to some, but it can definitely impact things like opening bank accounts, getting mortgages, etc. So, yes, having credit is not bad...but the act of getting and cancelling a bunch can be detrimental.

Cheers.