Originally Posted by Campag4life

Biggest mistake many make is the put a riser stem on their bike with the same length. First a riser stem with the same length has a shorter effective reach and as Robert mentioned, you need more horizontal reach if raising the handlebar. I would say most don't get this that raise their handlebar.
A comfortable handlebar position on a road bike is like coming home. If there is a common mistake on the road its with too low a handlebar and with the bar to close to the rider. This makes the arms more vertical and puts more pressure up the arms. Pros ride with not only a low bar but way stretched out. This reduces angle of attack of the forearms to the bars which reduces pressure on the arms and is also more aerodynamic as more vertical arms catch more air.