Like other categories such as best foreign-language film, best original song, and best short subjects, the potential Oscar nominees in the best documentary category are hard to predict because the nominees (and in this case the eventual winner) are decided upon by a relatively small group of people, each with their own sets of rules and regulations, minimum passing grades, pet peeves, personal friendships, et al.

Addendum (Nov. 18): So difficult to predict, in fact, that two of the films previously listed above — Michael Moore's Capitalism: A Love Story and Yoav Shamir's Defamation — were not even included in the Academy's Documentary Branch list of 15 semi-finalists for the best feature documentary 2010 Oscar. Also left out was R. J. Cutler's widely acclaimed The September Issue, listed below as a "strong potential contender."

Another strong potential contender is: R. J. Cutler's The September Issue (above), which focuses on Vogue editor-in-chief Anna Wintour's preparations for her magazine's 2007 fall issue.

And there's also Kirby Dick's daring Outrage, an indictment against several closeted anti-gay politicians.

Among the other documentaries in the running are (some of those depend on their actual release dates in Los Angeles/New York):

Alastair Fothergill and Mark Linfield's box-office hit Earth (above); Adam Del Deo and James D. Stern's Every Little Step, which looks at those auditioning for a Broadway production of A Chorus Line; James Toback's Tyson, about fighter Mike Tyson; and Matt Tyrnauer's Valentino: The Last Emperor, about the fashion designer.

Also, Marshall Curry's Racing Dreams (above); Davis Guggenheim's It Might Get Loud; Sacha Gervasi's Anvil! The Story of Anvil; Terence Davies' Of Time and the City, Aron Gaudet's The Way We Get By, and Lucy Bailey and Andrew Thompson's Mugabe and the White African.

I don't believe that Jonas Brothers: The 3D Concert has a chance.

Sources: All These Wonderful Things, Thompson on Hollywood