On Topic:
I agree with a lot of the comments about how the person with a knife carries themselves, and would add that it matters whether they are situationally aware (where they are, who is around, what else is going on, etc).
Yesterday, I was returning a duplicate gift for my kids at Walmart, did some other shopping, and grabbed some cough drops (due to an annoying cough that won't go away). As soon as the cough drops were scanned at the check out, I pulled out a knife and opened them because I needed one. I did not grab my Guardian 3 off my belt, even though it was more than capable and is my preferred knife. Based on where I was (next to a cash register a week before Christmas, most probably on camera), who was around me (a number of ladies and moms with kids), I pulled an Alox Vic Farmer out of my pocket instead. No one batted an eye, and I got a smile from the checker. If I had pulled a fixed blade in that situation, in this part of the country, someone (probably the checker) would have freaked out and the cops would have been called.
Yes, I changed my behavior a bit to not stand out or cause an incident. Yes, it was a conscious decision, which I did not like making. However, the highly probable trouble that was averted was worth the change in behavior, in my mind. Of course, YMMV.
Off Topic:
Let me know when those come out, in pink (like someone else requested). I would want to consider one for my little girl, and one as a gag gift for my wife. She would carry it, use it, and laugh every time because she is "not a delicate little willow" (her words) and hates the "pink and frilly" 'girls' marketing.
Enjoy