The rumors are true. Forrest Griffin will face Anderson Silva at UFC 101. As usual, when Dana White and the UFC are backed into a corner, they come out firing. The negative publicity following Silva's lackluster victory over Thales Leites definitely forced their hand. They needed to get Silva back into the cage and against a talented opponent. Griffin is a perfect choice. His fights are almost always entertaining and he's popular enough to sell the match-up to a large audience, something Silva has not been able to do yet.
The biggest winner in all of this is probably BJ Penn. With Griffin/Silva on the card, UFC 101 becomes a major PPV. He'll make quite a lot more off of PPV buys than he would have with Griffin fighting Thiago Silva. Penn seems pretty smart now for passing on UFC 99 (destined to tank at the box office).
From a style standpoint, I can see arguments for Griffin or Silva having the advantage. Griffin is a big Light Heavyweight. As St-Pierre/Penn II showed, size (and Vaseline) matters. It's difficult to imagine Silva being able to use much clinch work without Griffin tackling the hell out of him. On the pro-Silva side, you have Griffin's ability to get hit in the face by just about everyone he fights. He always reminds me of Rocky Balboa the first time he faces Apollo Creed. It's like he's purposely leaving his head out there to get hit. Do that against Silva and this thing won't last long.