I've been with Fotolia now for about a month, and one of the things that I really love above this site is that they let you know who downloaded your photos, by name and sometimes company.  This doesn't always tell you exactly what your photo is being used for, but it at least gives you an idea of where it's going.  It would be nice if some of the other microstock sites took their lead on this and did the same.  It can be done!