A friend uses a rack like that on the back of his suv. It's nice, but I'd plan on buying some kind of cable/chain/u-lock in addition to prevent theft.
We would love to find a solution that keeps the front wheel on but locks the bike up in the truck bed, and so far have been skunked. So we went with the Yakima Bedhead fork lock variety.
It seems like there's a huge market opportunity being lost here.
The only other idea I had was building a pvc rack like some shuttle monkeys use, then figuring out how to lash them down to the bed with a new York chain or something equally needy. Figuring out how to make that work without beating the bike up while bouncing along dirt roads was still an issue though.