By 1915, Slipher had shown that some of the nebulae had radial velocities in excess of 1000 km/s. At this time, the nature of the nebulae was controversial. In the context of what was known about the kinematics of objects in the Milky Way, the extreme velocities of the nebulae seem like a fairly clear indication of the extragalactic nature of the nebulae. Slipher himself pointed out that his velocities favored the Island Universe concept. But for some reason, his data did not have the impact on the controversy that one might have expected. I am interested in why some major discoveries do not have the impact that they deserve at the time that they were made. Sometimes they are too far ahead of their time and, as in Slipher's case, the discoverer does not really get the credit for the discovery even after its significance is understood. I will briefly discuss some other examples of this phenomenon.