Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
It's a bad idea.
Buying or selling miles violates the terms and conditions of most frequent-flyer programs. Consequences can include forfeiture of any (remaining) miles in the seller's account, and cancellation (with no recourse) of any award tickets obtained from miles that were sold.