How much of a Wiki article can we quote?

I realize Wikipedia articles are not under copyright, but I had this in mind:

Curtis LeMay originally posted about 2,100 words from the Wikipedia entry, which was way, way overlong. One paragraph near the end was highlighted, which indicated most of the rest of the quote was not necessary. The entry is something like 11,000 words, so he quoted about 20 percent of it. I cut the excerpt down to about 350.