Win an XBox every 10 minutes.
Under a Mountain Dew cap there's a 10 character alphanumeric code. Text this code (SMS) as the subject to PEPSI(73774) to enter this mobile marketing contest. There's a winner/auction every ten minutes.
Each time you enter a code via your mobile phone, you will receive a reply message letting you know your code was validated and added to your Account History
This is a unique combination for mobile marketing.
Yahoo requires that you register your mobile phone number first on a PC, and then asks you to check specific questions pertaining to solicitation on the mobile. Is this their idea of getting permission?
Here is Yahoo's mobile device privacy page
One line that caught my attention pertains to location based services.
"Yahoo! may use and store this information to provide enhanced location-based services as well as to serve location-targeted advertising"
I like the idea of "controlling" what mobile marketing campaigns you're being including in. This does eliminate the spontaneity of most mobile marketing campaigns though.