[czr80]

I don't think the (strong) version of the efficient-market hypothesis is defensible but Warren Buffet's track record is not proof that it is wrong - in a random market, given a large number of investors, some will do well purely by chance.

[aprescott]

Not necessarily refuting what you're saying, but here's an interesting take on "purely by chance" from Buffett, by analogy of coin flipping and getting a run of heads: http://www.tilsonfunds.com/superinvestors.html

[czr80]

That's a great article, thanks. I actually had the coin example in mind when I wrote the comment, but was too busy to write out the full argument!