Press ANYWHERE at the back of your screen, YOU WILL SEE the screen hits AT SAME LOCATIONS as the white spots. The screen lid design irritates the LCD, causing White spots:
"I pressed anywhere on the screen and I also noticed the frame hits these areas! So now where does that leave us all? A replacement screen will only have the same effect. Apple needs to redesign the lid frame so it doesnt press against the screen in the first place"
as discussed in Apple Support.
Apple is NOT the first company to come up with such defective design. Check out the defective IBM Thinkpad s of the Clemson University:
"Subject: White areas on screen
A few students showed me laptops that had small areas on their screens that were white or light colored. We need some samples of that. If your screen has a light area (not missing pixels - but light area the size of a fingerprint or a streak or larger), please reply to this message. We would like to replace your screen and send the ones with the white areas to IBM so they can research them. Even if you do not want to do this, please at least let me know your serial number so we can report serial numbers."
http://www.clemson.edu/cnews/article.php?sid=815
It seems we will see a new revision for 15" really soon.