This is an understandable sentiment, but clearly not true. Peer review is a good system of course, and peer reviewed papers are much more likely to be reliable than those not subject to it. However, to imply that no one not on the review committee can or should point out errors in papers is silly.
I bring this up because there's a great article at Retraction Watch right now about a guy who was doing a little reading in the journal "Water Research" when he came across a paper that addressed one of his pet interests. He was excited when he started reading it to find the authors seemed to share many of his opinions, and thought it was cool that they even used a lot of the same wording he would have......and then he realized the paper was his PhD thesis, with at least half of it copied word for word and attributed to another author.
The paper ultimately got retracted, and it looks like the journal handled it well. However, it's a great example of how peer review is not a fool proof system.
The world always needs people who keep their eyes peeled for error.