Mormitom is right--they're nice knives to own but it's not safe to carry, as there are ramifications.
But there's a question of enforcement as well, a neck knife wouldn't really be noticed casually would it? if you never give police a reason to give you a full patdown, turn out of your pockets, go through your collar, seams, hair, ... and your cavities, you should be able to escape detection. an acquaintance of mine carries an old fishing knife under his t-shirt, just tucked into his belt line, for stripping wires & other chores, and stays out of trouble.
i would carry a fixed knife if i could but dont' because i'm such a fine upstanding citizen…
I have considered buying one of those molded plastic neck sheaths for a kershaw leek (from ebay) but I already have enough knives on me, and i doubt reaching under my shirt and grabbing at some suspended knife would really be faster than going for my right front pants pocket. Is there a reason why you need a concealed stealthily carried knife? I prefer speed of deployment rather than concealability. I carry three in positions that can be reached quickly, and are only partially concealed. they're all recognizable as knives to someone with the knowledge.
As for concealable folding knives I like the smaller assisted opening Kershaw knives as the scales are flat (not taking up too much space in a pocket) and deploy quickly. Leek, Chive, Scallion, Centofante, Baby Boa, Mini Mojo. I know it's a plug but they're nice knives.
