Interesting article, and a good refutation for people who say that Wikipedia is "successful" simply because of how popular it is.
The problem of 'link spam' is real and growing, so it's reasonable for Wikipedia to protect itself. Some people are saying that the encyclopedia is now so dominant that links to it should henceforth be ignored by the search engines. After all, you don't google Google (so to speak) to find it. Is Wikipedia now in the same league?
One of the most useful concepts in technology is the 'success-disaster'. This is a product or service that is so successful that it overwhelms the organisation that invented it. The term was coined by the late Roger Needham, the great Cambridge computer scientist, and one of the wisest men I ever met.
Web 2.0 is riddled with incipient success-disasters because new web services can be created with very little upfront investment and, if popular, tend to expand exponentially.