In bold - wrong.
Most are. It's documented. Saying it isn't, does not make it so.
http://www.venomdoc.com/forums/viewt...ight=colubrids
If I may be allowed to quote form someone who has actually done research:
"Most colubrid snakes have very potent venom but produce very small amounts of it and typically have quite small rear fangs."
As for garters:
http://www.venomdoc.com/forums/viewt...light=sirtalis
Pay atterntion to WW's posts - that's Dr. Wolfgang Wuster.
http://en.wikipedia.org/wiki/Wolfgang_W%C3%BCster