I am the owner of both a 2000 Grand Am and an 2008 G6.
My Grand Am has 185,000 miles on it. I've personally put on no fewer than a half dozen sets of front wheel bearings. I buy Timkin brand from my FLAPS (friendly local auto parts store, a term I learned from the Grand Am Owners Club forums) with a 1 year warranty and replace them within that time period for free. I've been doing this every year for the last 5 or so years (and still have only paid for the original pair).
These cars have a notorious problem with their front bearings (the Grand Am's). I don't know yet about the G6, I just got mine this month, but considering the G6 is the successors to the Grand Am I would not be surprised at all if they also have this problem.
I have put the bearings on myself and I have also let 2 different mechanics/shops put them on for me, so I don't think it's something I am doing wrong. I am also quite knowledgeable about cars, I do almost all of my own work, including a timing chain/water pump replacement on my Grand Am last summer, so I don't think it's some other problem causing the bearings to go bad.
Also, in regard to the post about the part being on "national back order"... there should be plenty of non-OEM manufacturers for this part, like I said I use Timkin which comes with a 1 year warranty.