The thing is, the top journals are also _extremely_ loath to publish retractions. Give http://retractionwatch.com/2013/11/27/at-long-last-disputed-... if you haven't seen it before and note that this is a case in which one of the paper's coauthors has been pushing for the journal to retract it for years. In cases in which it's other scientists pointing out that the paper is bunk, you get situations more like http://retractionwatch.com/2013/07/04/retraction-of-19-year-... or http://retractionwatch.com/2013/06/19/why-i-retracted-my-nat...

And as for followup papers that contradict/correct the previous one, none of the journals make it easy to tell they exist or anything. So people keep citing the original erroneous paper. That last link in the previous paragraph puts some numbers to the scope of this problem if you look at it (16 citations for the retraction, 976 citations for the bogus unreproducible paper, 700 of the latter coming _after_ the retraction was published).