Hillbillly -
The problem is in the "common" names which change from place to place and person to person.
You are so correct! Common names drive me crazy when talking with anyone who only uses common names.
I, too have heard Datura called all three names that you have. I can tell you that I have never heard another plant besides Datura called jimsonweed but I have heard several flowers also called moonflower - including Brugmansia (very like a Datura) and Ipomeas (also called morning glory except this one blooms in the evening - hence the moonflower moniker!) Sorry if the spellings are wrong - I don't have my books with me right now!
First off, Datura and Brugmansias are related, but different. Daturas point 'up' (which is why they are referred to as Devil's Trumpets). Brugs hang 'down'.
The 'moonflower' moniker is given to some other plants, too, but Datura and Ipomoeas are the two usually called moonflower.
I have also heard both Datura and Brugmansia called Angel's Trumpet.
Or Devil's Trumpet, probably the Brugs are the Angel's.
ok i have a question. once upon a time i was told that datura and jimson weed were the same plant then i was told that moon flower was not the same as jimson weed now i hear that moon flower is the same as datura, i'm confused, could some of you botanists help an old cow puncher out please
Don't worry, it all comes out in the wash!

Jimson weed and some Moonflowers are actually Datura. Vining moonflowers are most likely Ipomoeas, a member of the morning glory family. Stick to the botanical names and you won't be confused (hopefully).