The fine print of a current Dish Network/Southwest Airlines promo:
"By providing your telephone number and clicking submit you authorize DISH, Blockbuster, or its representatives to use this number to contact you regarding DISH and Blockbuster products and services through an automated or predictive dialing system or prerecorded message system; regardless of whether the number is on any do-not-call lists or is otherwise registered as a wireless telephone number."This pretty much removes your number from the FTC's National Do Not Call List.
This clause in this contest is illegal.
By law, a contest must have an opt out, but never trust that if the contest is found out to be against the law that damage won't already be done.