If you were in a peloton with Petacchi on your right, Hushovd on your left, Zabel in front of you, and McEewen behind you, and the finish line were getting bigger and bigger, you'd be wise to make a break. Not all riders can close with the best. Some are better at "time trialing" the final few kilometers. Guys like Aitor Gonzalez and Jacky Durand come to mind.