This history animation service is not operating anymore.
Here's an example of Europe (the animation may only be visible after you click on the image and load the full-size version):
You could influence the style of image generated using some parameters (projection, background image, colour and size of dots, etc.) and select the time range for which you wanted the image to be generated. The database was updated with data from the newest planet file each week.
The source code for the "history service" is available in the OSM SVN (http://svn.openstreetmap.org/applications/rendering/history/) and is in the Public Domain.