Hi, I'm one of the professors who fails* students for using Wikipedia as a cited source.
The reason I do so is in the second paragraph of your own post. It's not a good primary source (i.e. something that can legitimately appear in a bibliography), but a great place to start from to look for primary sources.
In fact, I encourage my students to use wikipedia -- when starting their papers. But I explain to them that they can't finish their research there.
All that said, I'd love to see universities get involved in some sort of distributed funding mechanism for Wikipedia.
*that is, I fail them on the portion of the assignment where they had to do some research. Asterisks seem very popular on slashdot today.
What is algebra, exactly? Is it one of those three-cornered things? -- J.M. Barrie