Yeah, I have it too. I'm quite puzzled by it, but I'm having some other problems with my phone and they are offering a replacement. So i'm not sure i should worry about it.
What's really annoying is when you send in your brand new phone (with no dust) because of the rebooting problem and get a refurbished one back with dust! I'm getting more and more fed up.
Yeah - I had to swap out a Nextel 7520 several times before I got a decent one. Not due to dust but other problems. I'm not sure who is in charge of quality control at RIM or Nextel or both that just sends the refurb unit right back out without really checking it out.
Crap, I'm looking to dump my old 7100T and wanted to clean it up before giving it away. I was able to take care of all the scratches on the front using a couple abrasive applicants, but this dust behind the front screen is odd. Not quite sure how to remove it.
Might try using an old LP de-magnetizer to cancel the charge and then carefully tap the screen while holding the unit with a vertical orientation of the display so that it bounces off the side.
Blowing it out is bad! It will only introduce more particles.
Rubbing the screen will also build up charge and help hold the dust in place.