When you install the Post Page Associator plugin, an advertisement for the premium version, Associated Posts (PRO), is added to your list of installed plugins. The ad even show up on the list of inactive plugins.
If every plugin developer decided to spam various parts of the WP admin interface, it would be a disaster. We are lucky that a vast majority of the developer community seems to realize how crass this behavior is and has been able to resist the temptation.
I have no problem with developers asking for donations, and I have donated in the past, just don't muck up parts of the interface you have no business messing with.
Is there any way that a plugin that indulges in this sort of behavior can be censured by the WordPress organization? Maybe by removing the offending plugin from the official repository.