This is not something I came up with, half the forums I frequent have it.
I'm not talking about people who have to leave or take time from the site because of personal reason and just want to say goodbye to their friends.
I'm talking about threads where a person posts "I'm leaving the site because I'm dissatisfied with a feature!" they're attention-seeky "Beg me to stay, say how important I am!", they almost always degenerate into flame-wars, the person usually doesn't even intend to leave, and most of all they're disrespectful to the admins by being blatant attempts at blackmail. "do what I want or I'm leaving the site". That's just disingenuous and narcissistic.

Not directed at anyone specifically as I've seen at least 4 or 5 instances of this in a WEEK I've been on the site.
Including the incredibly disgusting "Buy this trade for x GB or I'll have to leave Lioden!"

I think i should be a bit more specific: you can exress dissatisfaction, you can make farewell threads, but dissatisfaction masked as a fake farewell thread should be against the rules.