Yes, risk. Clearly I was primarily speaking in regards to the TSA or military base brought up earlier, or anywhere it's illegal to even carry a pocket knife. A weapon charge will seriously F your life up. It's not a worthwhile risk IMO. It's a far greater risk than not having a weapon and needing one too. Anyone who disagrees with that is either unrealistic or hanging out in the wrong places. Is your daughter a trained knife fighter? If not she stands a better chance of catching a felony than using it to defend herself.
Also, yes, size AND effectiveness. You aren't carrying a ceramic chef knife in your pants. All these knives folks keep posting are cute little pairing knives at best. Can you kill with one? Sure, if you get really lucky or are skilled with a knife. Can you take on a properly armed opponent with one? Yeah... Good luck with that. If someone with a good sized metal knife comes at you and that's your response, you already lost. You'd be better served running away and shouting. The same goes with someone with a bat or a hammer or a gun or whatever. The scenario that little apple peeler gives you an upper hand is 1 in a billion. I've been stabbed. It sucks. A knife fight is a no win situation. Little knives suck as weapons. I carry one too when I can, but it's such a last resort weapon. I've even had one in my hand faced with a gun. I kept it palmed and didn't do anything stupid like think I could cut my way out. Neither of us was shot that night...
I'm really not trying to pick a fight with you, just being realistic... Is just bad risk assessment. Poor value/low upside for the potential downside. Get caught with it, while low risk, and you're catching a charge. It's clearly an attempt to skirt security. Unless it's in a bag with an granny smith you aren't selling that any other way. If you're so concerned that you need to be armed somewhere you aren't allowed to be and can't bring a legitimate weapon with you, you probably shouldn't wherever that is...
Now I'm rambling, sorry... on to other things... again, not trying to pick a fight just trying to throw out another point of view...