I've had friends steal from me on several occasions and then have their asses beaten.

Some guys tried to jump me once, they failed. Knives scare people off if they don't have them or when the one knife you do have is a pocket knife and they you're pointing it at pulls out a sheath knife.

I also fought to help a friend being jumped. He still got beat up pretty good but at least he got to keep his junk and not die.