What is this 512x512 picture?
Bad Quality Lena indeed, but the trick is that it's black&white - can be directly seen as length 512x512=32kB bit sequence.
It occurs that making bit sequence "looking like Lena" reduces the capacity only to about 0.822, what is about 26kB in this case - the visual aspect costs only about 6kB.
It has rather too high resolution for practical applications, but here are examples of lower resolution codes looking like a chosen black and white picture:
for example the central noisy code contains 800*3/4=600 bytes - making it look like the picture costs only 200 bytes.
Here is fresh paper about obtaining it (generalization of Kuznetsov and Tsybakov problem - for constrains known to the sender only): http://arxiv.org/abs/1211.1572
Todays QR codes usually contain only address - nearly nobody uses them because its simpler and quicker just to google or store/remember it. The situation should change if they would look attractively and have much larger capacity - even just out of curiosity motivating to get closer to make a clear shot to find out what interesting contents it hides. Todays phones have about 8Mpixels, so a well designed QR codes could contain hundreds of kilobytes - a ring tone, an application, a wallpaper ... even a huge poster could by the way be a QR code - we could imagine a marketing campaign where you need to collect some of them to get a prize ...
Todays QR codes are industrial standard - it's time to adjust them to everyday life ... increasing capacity and improving visual aspect is a natural direction of evolution.
What do you think of replacing today QR codes with nicer looking and more visually descriptive ones?
What other applications could you think of for this new steganography for which two colors is finally enough?
update: fresh discussion http://www.thenakedscientists.com/forum/index.php?topic=46597
update: presentation http://dl.dropbox.com/u/12405967/qrsem.pdf