Since no one else has mentioned it, I will. Too much crimp can be dangerous. Remember, the 9mm, 40, 45, and other straight walled rimless pistol cases headspace on the case mouth running into the step at the end of the chamber. If a case is crimped too much, it could wedge itself a bit past that step. This would drastically raise pressure, as the case would not release the bullet properly.
This degree of overcrimping would be difficult with standard dies for the caliber. But it is possible if one gets overzealous. When setting up the seating/taper crimping die, look to see if the case mouth is getting deformed or shaved. If it is, that's way too much crimp. And NEVER NEVER roll crimp a straight walled rimless pistol cartridge for a semi-auto pistol. Roll crimping is for revolvers with rimmed cases, or rifle cartridges. This would be hard to do anyway unless one was using bullets with a groove or cannelure. Cast bullets have them. One could overcrimp a soft lead bullet, too, to the point of being dangerous.