So just in the last week I have run into 2 or 3 panels that were wired improperly. Sure, some people will argue with me and say that electrical safety/protection is over-rated, but allow me to disagree-it is one of the most important things you can do to prevent fires in your home (definitely up there with dryer lint cleaning and keeping open flames away from flammables).
The homes that have these issues are usually older, mid-70's or 80's homes, with no recent updates to the electrical system. The problem I ran into is that the panels are not fed by a neutral wire, thus making the ground wire the "neutral" or in other words, creating a serious problem. In the case of an electrical fault at a receptacle, the current should flow back to the source (think: electric company power station) via the ground. If you have removed the ground wire (or made it a "neutral"), then you have removed that safety measure, making you a target for the current to use while it attempts to return to the source. It will usually find another path, one you didn't expect, nor desire.
Instead of getting into electrical theory, arguments, debates, or discussions, let's keep in mind two important things about electricity -
1. You cannot see it.
And 2. It can kill you.
Enough said. Keep your homes safe, folks!