It appears as though this change was made for the installation of a new time slot to be operated as flight 474. This may have something to do, I am assuming, with the additional service on the route JFK-LAX which commences July 1, 2010. They probably had to rearrange the times in order the add the two additional flights on the JFK-LAX route.
Hope that helps, I don't know with any certainty that this in fact is the case, but it is my best guess considering jetBlue is increasing service from LAX to JFK.
It looks like the only "shut-eye" flight jetBlue shows, is a connecting flight from LAX-BOS via JFK (674-1022).