Starbucks is halfway through its first major foray into mobile marketing, encouraging people to use their camera phones as part of a scavenger hunt.

Participants in the promotion - the "Starbucks Summer Pursuit" quiz and sweepstakes - receive SMS questions and reply via text or by sending a picture of the answer, writes ClickZ. Questions and clues relate to summer or the brand; for example, "Two p's, two c's and no h. I'm hard to spell, but easy to drink": (answer, "Frappuccino"). To join the promotion, players text-message "SUMMER" to 66268.

Starbucks is supporting the promotion with keyword buys, outdoor advertising, invitations distributed at stores and events, and an email blast to some two million Starbucks fans. Five players will be chosen at random for a scavenger hunt in New York City; the winner will receive a trip for two to Costa Rica.