I was going to add a reply in regards to the last few posts, but Krc beat me to it! I agree with Krc in regards to dust (etc.) vs. orbs. And just to add a bit, I don't believe that true paranormal orbs are that easy to document. I believe that a high percentage of orb pics are explainable. I, too, have also experienced dust being behind objects (or looking like they are behind something when they're really in front of it) and environmental orbs at a distance.
This doesn't explain away orbs, or course, and there has been some progress, I believe, in regards to distinguishing the true from the false. But orbs still are very tricky.