I interpret that as meaning they need to obtain permission first, as opposed to assuming that permission was granted when you chose to install the plugin, and allowing a method to later revoke it. I'd like to know if I'm incorrect on that, of course - before I end up wasting developer and moderator time. Let me know.
You're right though - it's a vast repository. I'm sure one could spend pretty much all of their time tracking down infractions and still never come close to keeping up. But there have been a couple of particularly egregious examples of link insertion that really have upset me lately. Meh.
Can't complain too much though - it is all open source, after all, and you always get much more than you pay for.