The first company to use this new feature will be Pepsi. During the Superbowl on Feb 1, they will kick off a huge campaign which will promote their products and iTunes at the same time (Article from Reuters):
"Special codes that can be used to redeem a free track through iTunes will be contained in bottle caps of 20-ounce and 1-liter bottles of Pepsi, Diet Pepsi and Sierra Mist.Steve Jobs also covered the campaign in his keynote speech last week (a Quicktime movie is available here, the Pepsi presentation starts after 50:27 minutes).
In all, 300 million Pepsi bottles will be wrapped with special iTunes packaging. Only 100 million bottles will contain redeemable codes.
"This historic promotion to legally give away 100 million free songs will go down in history as igniting the legal download market," Apple CEO Steve Jobs said in a statement.
Pepsi reportedly will pay Apple for each of the songs downloaded during the promotion."
Using digital items, like downloadable music, as incentives for these kind of sales promotion activities is a clearly no-brainer. Here in Germany, Coca-Cola tried it last summer with polyphonic ringtones and it was quite a success...