I carry nail scissors through BAA security on most occasions that I travel without checking in hold baggage, which is most of the time. For obvious reasons I won't say how I get it through and although the blades on them are only about an inch long (but against BAA rules) I'm pretty sure I could get a much larger blade through using the same technique (which of course I wouldn't even attempt).
So what's really the point of the current security procedures? Meaningful screening to prevent a future terrorist attack or being seen to be doing something, however fallible it can be demonstrated to be...