A couple of days ago I powered on my 15" MBP and noticed this "hair like" line coming from the left edge of the screen. It was about 1/2" long and was bent at the end. I was convinced it was dead pixels. Tried a few screen exercise programs to no avail. Turned off the computer and turned it back on and it was gone. The next day back again, but twice the size. Off to the Apple store and to a genius appointment. He looked at it and said, it looks like a hair. Took it in the back, to the repair tech, and came back to tell me "it is a hair that got there during manufacturing. It is nothing you did." I was relieved, I could not remember trying to shove a hair between the glass and the LED's of the display. They said we will replace it and we will need your computer for two days. Two days later, I have a new display and all is well. Who knew that hair can get in between the glass and LED during manufacturing? You would think that they are wearing the Tyvek suits with the hoods, etc. while manufacturing a computer component. Anyways, just thought I would describe this situation in case anybody else notices a hair like thing behind their screen.