gcurling said:
Michael Jackson
Hugh Heffner
Rush Limbaugh
Ellen DeGeneres
Tom Cruise
John Edwards
Arnold Schwarznegger
Laura Bush
Hillary Clinton
Mel Gibson
Madonna
Dr. Phil
Martha Stewart
Donald Trump
This is absolutely embarrassing
How about:
Harriet Beecher Stowe
Georgia O'Keefe
John Marshall
George Gershwin
Babe Didrickson
Robert Goddard
WEB DuBois
Noah Webster
Fiorello LaGuardia
Edwin Hubble
Irving Berlin
Leonard Bernstein
just for starters, and several hundreds more that should go on before any of those names.
No question there is a lot of room for debate, that's what makes these sorts of things fun. Usually lists like this are more fun with sports, since sports by nature are a pastime and less serious, therefore debate doesn't usually get too heated.
On your list of questionable people, I agree, most of those should not have made the top 100. I would disagree to an extent on these:
Rush Limbaugh - love him or hate him, he
made a new medium - talk radio (which you may love or hate

)
Arnold Schwartznegger - a self made man who really is a rags to riches story
Hillary Clinton - I'm not a fan, but she is a
huge hero to many
I'm not sure where those accomplishments should put them, and I don't think any of them made the top 25, which I think is appropriate. Some on your list certainly would surpass them.
Now, regarding
your list, I would take issue with Georgia O'Keefe, George Gershwin, Babe Didrickson, Irving Berlin and Leonard Bernstein, as they were all basically artists or entertainers, which you seem to dismiss from the other list (to which I agree). I suppose some room could be made for one who truly pioneered in their field (maybe Babe for women's sports?)
I also take exception to one name you suggested: W.E.B. DuBois. While he was certainly brilliant and accomplished, he was also a communist and considered Stalin a great man. He was, I think, in his 90s when he joined the communist party and offered statements in support of Stalin (some I believe even after many of Stalin's human rights violations were well known). It's too bad his final years did tarnish his image. I believe he also renounced his US citizenship, which may have made him ineligible to be called one of the top 100 "Greatest Americans".
I very much like your additions of John Marshall and Harriet Beecher Stowe, and of the scientists Hubble and Goddard. And I could have sworn Webster was actually in their list, but I just double-checked and he isn't.
My additions, being the geek that I am:
John Vincent Atanasoff - pioneered digital computing, first to use binary system for computing
Marc Andreesen - WWW pioner, would prefer Tim Berners-Lee but I don't think he's an American!

Vannevar Bush - if Andreesen too young - Bush's ideas in the 1930s led the way to hypertext (but he also had some really odd ideas - which I suppose, if you have a lot of ideas, isn't strange)... Perhaps he is trumped by the fact that there are already too many Bushes.
