OK OK OK... I personally don't buy it, but there's a thread on the NW board which references 2 people hearing that people have been offered:
- status match (including one to EXP)
- match whatever current mileage balance is in his NW account
- provide an Admirals Clum membership if currently a NW WorldClub member
http://flyertalk.com/forum/showthread.php?t=544780
Honestly, I think all 3 are a total load of cr@p. The status match is at least plausible as it has been done before (albeit less on AA due to the challenge), but matching miles and a club membership??? Never...