Originally Posted by Treefox
The long horizontal sort allows you to adjust your rear wheel so that it's as close to the frame as possible without touching (as this could vary with the tire), thus improving aerodynamics.
Some bicycles still have this - - I think the fancy Cervélos...?
its not aerodynamics that short chainstays are good for, its shorter wheelbase, therefore less flex. however, super short stays make a bike handle like crap, see cervelos and how many crashes they are involved in. short chain stays good, super short, bad.