If the cost (in terms of reputation) of printing a paper and subsequently retracting it is lower than the cost of rejecting the paper in the first place, a journal is actually better off printing a dodgy paper and then backtracking later. Ultimately these journals are money-making functions of a business enterprise so they'll usually do what they can to maximise profit rather than quality, apparently even if that hinders the science.

although I think it's fair to say that not all retractions are the result of fraud. I'm not sure about the ins and outs of this case for example http://retractionwatch.com/2014/12/26/nature-cell-biology-in... but I think it looks like a straightforward revision due to more up to date information. This seems to be a good example of how science should work i.e. scientists posit theory, scientists receive new information and update or revise theory in light of this.

do you think this is just a by product of elite journals being targeted more often, rather than a conscious effort to optimise profit?

The more elite the journal, the more "important" it's likely a paper in it is. If the paper is truly important, people will try to build upon it, and in the process discover problems with it.

Contrast to "less elite" journals which in part serve the "publish or perish" market, and are therefore less likely to have material other people care about. The smarter cheaters will obviously game that general concept.

its definitely an interesting problem. i think its possible that the elite journals are 10x better at detecting fraud but are 100x more like to be targeted. i wonder how we could collect data on this if at all possible