"If a number registrant fails to appear on the 'AWA member list' for 2 consecutive financial years (July-June), the number may be made available to someone else."
see sailnumber state rules page

363 numbers fell into that category @ 01/07/2011

Two lists have been collated, displaying the affected sailors and numbers:
1) Name Order, www.windsurfing.org/files/info/AWA_Cull_Names.pdf
2) Number Order, www.windsurfing.org/files/info/AWA_Cull_Numbers.pdf

Both lists display a field indicating last membership season, and the State where they joined. Numbers marked 0708 and earlier have until 31/12/2011 to renew their membership and keep their number. Those marked 0809 have to renew in the 2011-12 season to keep their number.

For members wishing to change their existing number (to one of the expired numbers), please apply via your AWA State rep, AFTER the respective cut off dates (see above). Earlier applications will not be accepted.