@Setanta,
I have to tell you I did a search and man what did I come up with as being classified as bad tippers:
Canadians
African Americans
Scandinavians
Brits
Church crowd
Women
Middle aged guys - and this guy said the same aged women were good tippers?
Fat nurses
Real Estate Agents
Almost anyone visiting in a tourist destination
Brazilians
Small european countries
germans
asians
less sophisticated southerns
working class uneducated people
trust fund babies
Slumdog millionaires (indians)
old ladies
The odd thing is one waitperson would say jewish were good tippers and another said they were not, or other groups.
Other most said gay and drag queens were great tippers - I didn't see any that said that group was bad.
Just read through some of these they are quite funny
http://waiterrant.net/?p=1597