I have had several athletes (and coaches) ask me about wide grip bench press (i.e. hands more than an inch outside shoulder width) and whether or not it's appropriate to use in the weight room, especially for young lifters.
In order to effectively and safely generate lots of force, we have to cultivate a stable and organized environment rather than rely on our passive structures (joint capsules, ligaments, etc.). The inability to generate sufficient stability in the wide grip bench press is not a good recipe for those attempting to throw up some serious weight.
** I should mention that I am all for changing grip width to vary the stimulus but not at the expense of decreased stability and ultimately decreased performance and skill transfer which is what really pisses us off (not to mention your shoulder and elbows.). My athletes have to demonstrate active stability and excellent shoulder internal rotation range prior to varying grip width.
The other HUGE advantage to setting the shoulders (creating shoulder external rotation against the bar) is that it optimizes the length-tension relationship of the pec major muscle allowing it to have sufficient capacity to contract forcefully throughout the whole range. Google the pec major and you'll see that it's fibers actually spiral onto its insertion on the arm, so by creating an actively stable shoulder we can open up that anterior compartment and take advantage of the pec's considerable cross-sectional area (which increases force). With the wide grip, we lose that tension and you'll see this with an athlete when he's unable to finish at the top of the press.
Seth - power farmer - Oberst