The generally accepted rule of thumb is that the shutter speed must be the same or larger than the inverse of the focal length.
As is, it seems that it makes no sense as is:
On a 24 Mpixels full-frame camera, at 100%, the blur from camera movement will be more visible than on a 10 Mpixels full-frame camera.
A photo intended to be printed small can have slight blur at 100%: nobody will see it when scaled down for printing. When doing a high-quality large print, even a small blur will be noticeable.
Image stabilization (vibration reduction) affects the blur when shooting handheld.
The blur will not be the same on a cropped vs. full-frame sensor.
I imagine that the rule of thumb appeared first when there was no DSLRs yet, and photographers were talking about SLRs with 35mm film. Is this that fact that makes the three of four points irrelevant? If yes, what about the second point? If not, what is the origin of this rule?