The person who uploaded photos of what appears to be the Harry Potter Deathly Hallows book is better running now and trash his Canon.

The Times reports that the serial number of the Canon camera used has been found in the Exif meta data of the distributed Potter book photos. The leaker used a Canon Rebel 350. Canon says that if the person has once serviced his Canon than the serial number is registered and they could identify the owner.
The 350 is most likely 3 years old, so chances are high that the camera has been serviced.

What that story just makes clear again is that photos you upload to the net have all kinds of information that can link back to you. If you want to be safe strip the meta data before uploading stuff.