Many people call all hollow-point ammunition "cop-killer bullets", because of these: http://en.wikipedia.org/wiki/Black_Talon
Many bullets, fired at a proper distance and with sufficient powder, will pierce Kevlar. Hollow-points don't possess a special ability to do so.
New Jersey, I believe, is the only state to ban possession of hollow-point ammunition by civilians. It's probably the most-commonly carried ammunition by civilians (in other states, of course), because the risk of over-penetration and ricochet are greatly reduced.
I know I recommend to students that they carry hollow-point ammunition for personal defense (because of the reasons listed above), and shoot predominantly full metal jacket ammunition for use at the range (due to reduced cost)

What is the point of rules that are not enforced?