The actual benefit for this promotion varies from person to person, it can be anywhere from 1 free reward night for general / silver members, to up to 25,000 bonus points for staying 20 nights from June 1 through August 31, 2009. The exact offer will be given when you register.

Earn extra Marriott Rewards® for a dream getaway

If you ever needed a vacation from the ups and downs of everyday life, this is the time and here’s the way: Stay at Marriott
June 1 through August 31, 2009 and earn extra Marriott Rewards toward your own dream getaway.

Register by June 30, 2009

https://www.marriott.com/rewards/promotionRegistrationInstructions.mi?promotion=SUM9&psrc=MRTR