Personalize your cover no longer applies only to mobile phones. Publishing company Penguin is currently running an online initiative which allows readers to design the cover of six masterpieces (The Picture of Dorian Gray and Crime and Punishment among the others). The best designs will be put into production, and will become real book covers. As I already said in the past, I love this kind of marketing ideas to stimulate user generated content, as they offer people a real added value. Reward consumers with something they cannot get themselves (and always exceed expectations!).
On the website they also say that, according to consumer research, when we decide whether or not to buy a book, cover design is always the most important thing. Unfortunately, I have to agree. If I don't already know the author, and I buy a book based on the "inspiration" of the moment, the cover does play a role in affecting my choice.