The point is this:
The internet is superior to a book in that the information is interconnected and browsable in any direction, much more easily than in books. And there's a lot of good reference material out there on the web-- Wikipedia alone is worth the cost of entry IMHO.
Wikipedia is superior to a book in that it's larger, much more interconnected than almost any book, and easily, quickly browsable. While it might not be ideal for medical students doing a research paper for a final source, here we are talking about children using the web to learn. I'm not sure I understand how your medical education experience is directly relevant to that.
Overall, I have to say that Wikipedia is a more useful general learning resource than, say, the Encyclopedia Britannica. While it contains some inaccuracies, at a higher frequency than a standard encyclopedia-- as well as other faults, such as some biased information-- it also has much, much more information on the whole, and much more unbiased, correct information. As an information hub which is also to some extent an authority, it can't be beat.
That isn't to say that information shouldn't be verified, or that children shouldn't be taught to verify. I think it's a little off topic, though you're certainly right. The topic is whether the web in general is a useful learning tool for kids; it is, and Wikipedia is a good example of a part that's useful for that.
My main reservation with letting kids use Wikipedia is not the accuracy of the content, but the appropriateness of some of the content.
