Hey Vis (Uninvis, that makes you Vis, right? 😉 --
It's happened to me, as well. Discoloration of the exact tyoe you described -- little black dots -- on either side of the trackpad, preceisely where I rest my wrists when I type. I actually did wipe that area down after each use, but I use it a lot, for extended periods of time, and it seems to have made no difference. I first noticed the problem about 6 months or so, give or take, after getting my PB, and it progressively got worse, slowly but steadily.
I've not bothered to go the AppleCare route -- it just wasn't worth it to me, all things (time & effort to convince Apple to cover it, having someone open up my PB when not absolutely necessary, loss of PB's use while they did so, degree of actual harm suffered quite small and of no impact on actual functioning, etc) considered. But, clearly, that's a very personal calculus and other people's opinions on the subject likely vary widely.
I effectively solved my issue (and stopped the damage from getting worse) by picking up a wrist rest cover up called the "Wrist Rug."
http://www.powersupportusa.com/products/rr.php?category=pb I got the dark gray model, it fits like a glove and I no longer notice the discolored areas, nor do I think the problem is getting any worse, since my wrists no lie on the wrist rug and not on the Aluminum and the Wrist Rug seems to absorb all my perspiration.
It's definitely a flaw in the materials, IMO, I mean something this new should not show this kind of damage, IMO. After all, it's not like I'm some kind of Kimodo Dragon hybrid or nothing, oozing toxic, corrosive sweat, just the normal kind, I swear. And I tidy up after myself and everything. Sheesh!
But, no matter, I've actually convinced myself that it just adds to the uniqueness and character of my PB, which remains far and away the absolute best piece of computing equipment, nay technology, that I've ever had the pleasure of owning. And the damage, such as it is, is all cosmetic so far as I can tell, and I'm not looking to resell anytime soon (if ever), so I can deal.
Good luck, however you choose to proceed.
-- JDee
EDIT: Oops. I just noticed that this post was in the 17-inch PB category and when I double-checked, I noticed that the Wrist Rug doesn't seem to come in the 17-inch variety. (Major oversight on their part if you ask me.) Oh well, you might try Marware's Protection pack, whcih comes in all three PB sizes and includes a screen cover as well as wrist area protector:
http://www.marware.com/cgi-bin/WebObjects/Marware.woa/4/wa/selectedCategory?cata logCatID=181&wosid=n6S248HChVFen084EdOzD0
-- JDee