Growth hacking might be a buzzword. But to me, it means coming up with a unique and viral way of attracting users to your product. There is a lot of unchartered new territory in marketing - social media being a big one. (turntable.fm had an interesting user acquisition route, I'd call that growth hacking)
Personally, I'm excited to see the new and innovative ways in which marketers will leverage these new technologies to reduce the cost and increase the speed of user acquisition.