Oops, I replied on the other thread...but here it is, FWIW:
Some schools do, some schools don't. I have never heard of an in-state applicant being less likely to be admitted, but some state schools are required by the state to have a certain percent of the class filled by state residents. Thus your chances of admission are improved if you're in-state, and working against you slightly if you're not. This is the case at UVA, for example, and why I am glad I am a VA resident! See Montauk for more info.