Thought I'd clarify generally a little bit. QR codes definitely have a lot of advantages over Meshtag - and they're perfect for what they do. I'm by no means suggesting this could "replace" QR codes.
Where Meshtag fits in is that it's aimed at users and not companies. I think a large reason most people don't scan QR codes is because they assume they're just trying to sell you something. But if you saw a meshtag that somebody drew on a wall somewhere, wouldn't you be curious?
Also, thanks for all the feedback! I have dreamed of being on hacker news since I started coming here. Any UI/UX designers in the Boston area, hit me up if you want to get involved!