Bob,
when I see "signature" I read "expensive".
Or, if I'm feeling a little insecure or shaky that day, I read "You're not wanted; this means YOU".
Probably a sound marketing approach, though. If "signature" registers as "expensive", I think the would-be consumer has 3 ways to react, i.e. "I want in", "Ah, not for me", or "Not for me, but I STILL want in; how can I get in? Please, someone let me in."
Grabbing the attention of 2 out of 3 potential customers with one little word seems pretty impressive!
Of course, I probably have no idea what I'm talking about; as I've said before, I couldn't market bottled water in a desert.
Peter