How Reliable is Wikipedia?

The taller of the short people is working on a research project on Ruth Wakefield, the accidental inventor of the chocolate chip cookie. She's finding few resources in the public library, so we did a web search and pointing to the results, she tells me that her teacher has told her that ask.com is to be considered a reliable source, but not wikipedia.

I, too, tell my students not to go to wikipedia as an academic source, but then a college class in philosophy is in part an experience in learning how to be a scholar, how to find and interpret texts. Encyclopedias of any sort are fine for factual purposes, but when you are working through complex arguments and living debates, you need to engage the participants, working through the primary and secondary literature.

But wikipedia is coming to be the icon for untrustworthiness, the used car salesman of the knowledge world. The internet is the intellectual version of the wild West, anyone can say anything and they do. Then it's out there. Wikipedia, because it is a wiki, is employed as the symbol of this factual lawlessness of this opposition to intellectual authoritarianism where the sun never sets on the Encyclopedia Britannica, despite having in place safeguards to avoid as many problematic changes as possible.

I've found it very useful for acquaintance type fact searching, for giving a context to something I had a vague sense of, in other words, exactly the sort of thing you go to an encyclopedia for. So, the question is whether it is deserved or a bum rap. How reliable is wikipedia?