A friend of mine started playing with the group request. And we noted that its possible to spam notifications if the group owner keeps declining the request. So my idea is that with a cooldown period. In that period the user cannot request to join the group. This is just to avoid the spam of notifications the group owners can receive.
I wonder how this works elsewhere. If I added you as a friend on Facebook and you declined, am I allowed to try again?
@psychobunny I cannot speak for Facebook or similar social networking sites, since I'm one of those anti social beings that only uses Steam and Skype 
those services of course have the block button to completely avoid the user in question.
@psychobunny In Facebook, after declining a friend request, a "Mark as Spam" button appears. If that user is sending you multiple friend requests then you can click on that button.
