The mass-marketed pop music compilation has come a long way since the days of 12-track K-Tel vinyl collections like Dimensions and Hit Express. Once a useful tool for listeners who just wanted to rock out to Styx's "Mr. Roboto" without committing to all of Kilroy Was Here, the modern comp has become a sort of disposable iPod for the MP3 generation, providing hours of music for a very reasonable amount of money. The Now That's What I Call a No. 1 installment of the hugely successful Now That's What I Call Music! series is the perfect example. Discs one and two are stocked with the usual suspects (Adele, Katy Perry, All Saints, Robbie Williams, Coldplay), while disc three is relegated to the "oldies."