There is no way to track who buys or sells Kellog's advantage certificates (unless you do it on Ebay). If there is not tracking method on how you acquired the mileage certificates, and you send a bunch in with your newly opened account, how would AA be able to tell that you bought the coupons?---AA can't. The risk is close to zero.

I find the rules that AA imposes on buying/selling miles too be very exteme and a feeble attempt to protect their bottom line. Stray miles have no value. 25000 miles have limited value and 50000==>125000 miles have extreme value. By not allowing people to pool miles (through buying/selling) they are limiting the value of all of the miles out there. Since over 50% of the miles given out each year are sold by American to partners (AA makes 100's of millions from this) [the rest are from actual flown and bonus miles], AA is getting rewarded by selling miles but limits the value by not letting people buy/sell them.

I fail to see what harm it does to AA to allow this. All mileage awards are capacity controlled so they are not going to be giving away seats that normally could have been sold.

It is the same logic that keeps people who buy the tickets from earning the miles or if you buy two tickets (for comfort or whatever) on the same flight for yourself you only earn miles on one of the seats--not both.