[MR4D]

That's true only if you believe in efficient markets. There is significant evidence that they are not. (Google "EMH disproved" and pick whichever reference you'd like)

[eru]

Depends on how strong you like your Efficient Market Hypotheses. The strongest version "markets know the future" is obviously wrong. The weaker version that say something like "it's really hard work to beat the market" are obviously right.

I invite anyone who disputes the weaker versions to go and make a fortune in trading. All the "EMH disproved" nonsense is mostly that: nonsense.