I think if they can successfully do it once, they can do it 2, 3 or 10 times. It's not really a delay of the inevitable, but it is likely to repeat itself a lot.
I think it still helps weed out the trolls. Trolling, after all, is about maximizing annoyance of others with minimal effort. If someone has to go through multiple accounts (with multiple email addresses, minimum post counts to gain credibility, etc) to annoy someone who only has to report them once as a suspected alt account to start the process over, they're really trolling themselves more than the rest of the board.