I can not agree with the last few posts.
1) Qualifying is a skill that does NOT necessarily equate to racing speed - I give you Trulli as a shining example. He is (in)famous for qualifying well, then acting as a mobile chicane during the race. We are all familiar with drivers that are better at qualifying than they are at racing.
2) The car that qualifies on pole is NOT necessarily the fastest car in racing conditions. Run a very low fuel load and you can get on pole, even if under racing conditions (a reasonable fuel load) you will only be able to hold up the parade.
3) Car setup can artificially influence a car's starting position. Run a very low drag setup at a fast track (Monza, for example) and you might get pole, but not be competitive in racing conditions.
4) There is an element involved that is not related to driving skill or car speed. Traffic can prevent a fast car from qualifying at its true potential.
I think that's enough (but by no means an exhaustive list) to illustrate my point.