Slight correction to this statement
"In the United States, many bars and restaurants serve Weizens, especially Hefeweizens, with a slice of lemon or other citrus fruit. This practice is not widespread in Germany and many serious beer drinkers consider it to be offensive. "
This is nearly correct. I come from Northern Bavaria (Weizen is a southern German style) and grew up with Weizen. Kristall is _always_ served with a slice of lemon in it. Hefe never.