As we all learned from Fight Club, there is a formula that automakers apply when deciding whether they need to do a recall. Hopefully it isn't one quite as callused as the one from the film, but BMW applied some sort of formula to decide whether a recall was needed for the faulty high pressure fuel pumps used with N54 engines. To BMW's credit, they did address the issue somewhat by extending the warranties for the affected vehicles.
ABC (and quite a few others) decided that this wasn't good enough and aired an expose which forced BMW to go ahead with a recall. It seems that a new factor has to be added to the formula. In the past, automakers didn't always have to do recalls, since those affected weren't usually talking to each other much. In the internet age though, gathering damning evidence is much easier, and the PR cost has to be considered.