The Short Answers To Every Matt Cutts Video
"Does Google use EXIF data from pictures as a ranking factor? Potentially, yes."This is a simple, but brilliant optimization.With the Manufacturer & Model info from the tag you could make an educated guess about professional vs. non-professional photography and draw conclusions about website's intent.With the date & time you've got relevancy of time beyond just search results. EG if you're optimizing for freshest / relevant content a "new" article that contains a recent picture with positive PR signals could outrank another "new" article that is using old pictures.With geo-data you've got an obviously powerful signal.And on and on.It is kind of crazy to think about the sheer # of breadcrumbs we leave online for GOOG (and, ahem, other organizations) to learn about us with.PS -= This is hugely useful resource, thank you for submitting!