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)
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