http://www.the-dma.org/guidelines/sweepstakesdosdonts.shtml
"A "sweepstakes" is a game of chance one plays voluntarily and for which one is not required to pay anything to enter in order to win a prize.
Sweepstakes mailings must disclose:
That a purchase is not necessary to enter, and will not improve the chances of winning. These disclosures must appear in the mailing, in the rules and on the entry form and be very easy to find, read and understand;
A name and business address where the sponsor can be contacted;
The estimated odds of winning each prize. If the odds depend upon the number of entries, the stated odds should be based on an estimate of the number of entries;
The quantity, estimated retail value and nature of every prize;
A clear statement of the payment schedule of any prize. For example, if a $1 million prize is to be awarded in equal payments over 20 years, the disclosure should indicate that the $1 million shall be paid in equal amounts of $50,000 per year for 20 years starting in 2000. "