Cameos have always been an excuse to get people to watch. It's a trick to get the simple minded folk to watch something that they probably wouldn't otherwise.
George Clooney cameo'd in an early episode of South Park, and Stone and Parker had him be a dog. Clooney did it anyway.
FightingSeraph
You should read my post titled "My List of Tacky Flash Trends" as well as my "Things on my mind" rants. As for actual voice actors, I'm ok with Egoraptor; whereas I think Rina-Chan and Tomamoto are stale and overexposed. Maybe we should team up sometime.