One of the advantages of the Vita that's often touted by Sony is its Crossplay ability with the PS3. Essentially, certain games available on both PS3 and the Vita can be picked up and played on either console, picking up from the last cloud save.
The only issues with the Vita's Crossplay abilities are cost and limited availability. Only a few games are available for Crossplay between the PS3 and the Vita. While Crossplay is convenient, it probably isn't enough to convince the run-of-the-mill customer to buy two copies of the same game at full retail price.
Sony's finally figured this out and has implemented CrossBuy. This means that when customers purchase certain PS3 games, they'll also receive the same game for free on Vita. Unfortunately, this promotion doesn't apply to current Crossplay games, so the only CrossBuy games thus so far are PlayStation All-Stars, Sly Cooper, and Ratchet & Clank QForce.
No doubt the Vita's slow sales have forced Sony's hand in this. We can only hope that more games get added to the Crossbuy lineup. Being able to take full advantage of the Vita's Crossplay features without having to hit the buck is a boon that's sure to draw more customers.