IMHO Depending on your setup it could put the weight behind the front hub as opposed to over it. You want your weight over the front hub for the best possible control, a shorter stem might put you behind the hub creating the sensation of pushing the wheel while turning.... it could be misconstrued as being twitchy, but still better than being ahead of the hub.

A stem that short means the frame doesn't fit, or you have some funky proportions.