This seems like very clever marketing, and OTCS approves. The cards will be "collectable" and feature various images of Lennon. And because it is being released during the holiday shopping bonanza, consumers are likely to grab these up along with all the other gift certificates they will already be buying (and not have to carry around all day!).
The real question is: does this create a conflict of interest with Starbucks' Hear Music record label? More poignent is the fact that Paul McCartney, Lennon's former band-mate in The Beatles, is the Hear Music label's signature artist. Notwithstanding any contract disputes with McCartney's former label (EMI), what benefit is there to joining Hear Music if your old label can sell compilations in the same limited venue, with nifty packaging that benefits both your old label, and your former opposition in a trademark dispute (Apple iTunes / Apple Records Ltd.)?