Water proofing outer blocks of new basement

Hi
I have heard that you can water proof outside basement blocks with a kind of a rubber sheet?
What do you think about that, since a friend of mine says its much better just to spray tar, and that any moister that will get trapped behind the rubber sheet can be a source of trouble...
What method do you prefer?

other than tar, they do make another product that forms a water barrier, and works on inside and outside.