Poor Man's Photo Geotagging

Picasaweb's new face recognition feature got me thinking: if every public sign in the world included a QR code with lat/long info embedded in it, then photo sites could scan for them in pictures and automatically insert geotags into the EXIF data. If geek Good Samaritans carried around combination GPS/label makers, they could obsessively deposit such codes as they walked around -- a sort of beneficial graffiti.

Update: I think this could easily work. I encoded a message in QR code, printed it out, and stuck it on a wall in the house. Then I took this picture of it:

Then because of size limitations on the online QR code recognition site I tried, I cropped the image:

Finally, submit to Google's ZXing site, and it worked.

Looks like some other people have come up with similar ideas (dencity is one). But this approach is a little different: rather than requiring users to run specific software on a cameraphone or otherwise actively try to parse the codes, this software could run automatically on Picasaweb and insert appropriate tags if it encountered QR codes following some sort of compact microformat.