The stickybits value-add is providing the infrastructure for a social version of what you described. You can set it up with absolutely zero technical knowledge (a key factor that people on HN can easily forget about -- don't forgot about the normals)
Of course anyone could whip up a free QR code that encodes a URL to your website/webapp/wiki/whatever and get the same thing more or less, but YOU must get the code and put the it on a sticker, YOU must build the wiki, YOU must integrate twitter/foursquare/facebook/geocoding, etc). That sounds like a fun project actually, but a normal company wanting that will have to put up big bucks to a developer to make the system. With stickybits, you buy some (overpriced) stickers, and all the features I described above are available to users with a complexity equivalent to texting. So, this concept is anything BUT weak. Simplifying a process is really, really important. When the iPod first came out, there were a lot of technically better options, but the iPod/iTunes combo was so easy to use that it crushed the competition. The cool factor was there too, and I don't know if barcodes will ever be considered cool, but that's another thread.
As far as making money...of course they will try to make money. It's a company, not a non-profit. I presume the money is in the data, much like bit.ly. Stickybits will be able to see who is scanning what codes, and where that's all happening. That information is ultra-valuable to any company trying to sell or promote something. In fact, I would not be surprised one bit if the prices of those sticker packages approach zero, because the real value is in gathering data, not selling stickers, and free stickers will help the userbase grow faster so a competitor doesn't steal their lunch.
The biggest hurdle would be getting people to adopt the stickybits app, or more generally getting other apps to adopt the stickybits API. The advantage of QR codes is that the format is standardized and widely adopted (well, relatively speaking). The best use-case would be using a QR code when encodes your company's website or whatever (NOT a stickybit code), but then scan that code with stickybits to add the cool social features. Then you hit all audiences: stickybit app users get to see the social comments and check-ins, while the information degrades gracefully for standard QR readers still can understand the underlying URL.
(Billy, I think it would be great if the stickybits app was able to decode QR codes and show that data, instead of only showing comments and the title. I guess currently you'd make a QR code, scan it with stickbits and, from the app, set the title and first comment to the content encoded in the QR code.)