Reasons to remove people from FL

Hi, this may be an odd topic, I've been trying to look for a list of reasons on google, but seems like there's never been threads as such, just "how can I remove someone from friendlist", "why don't I see him any more" etc.

So I've had someone remove me recently in a situation where I don't get what the problem might have been, don't have the slightest idea.

In the past I've come across the following main reasons:

1) most typical: you don't talk with someone often, in fact very rarely
2) "business contacts": you add someone to sell or buy something, this includes boosts, and when the thing is done one of you will remove the other
3) friendlist full: someone has lots of friends already and hits the cap and deletes some
4) ban which disabled real id: usually doesn't happen but I had it happen once, someone lost all his friends cause of this and as a matter of fact, when I asked him what happened, re-added me
5) the account owner wasn't the one deleting you: had this with a friend as well, don't want to go into details but someone who had access to his account deleted me, so only understood the problem when I e-mailed my friend

This has never happened to me so far, but I've tried to read back if I might have said something wrong etc. but seems all very normal.

Now all of these reasons seem very odd to me in this situation, do you know of other typical reasons for removing people?