no offense to those who have the GM Bed Extender, but for hauling a motorcycle, you are MUCH better off with a Ready Ramp, just used mine today to haul a pal's 2007 GSXR1000. A Great long ramp (you need length so it isn't too steep), which stores easily in the bed when not in use because it folds, and then it becomes a great bed extender (straps click into the gate lock mechanism and cinch off on the unit, and other straps hook over the latch pins and cinch off on the gate.
Wish I had taken a pic, but mine looks just like this:
I have tried other ramps, this one is one of the sweetest ones out there (the way it folds up makes it the easiest to store) plus the fact that it functions as a bed extender is great (let's face it, the bike is cinched down by 4 straps, but you need the peace of mind of having the gate back there). Plus, if you have other gear in the bed (such as you would if going to a track day) you want to keep it from sliding out. And you don't need to drill into your bed or mount brackets.
http://www.readyramp.com/