I would rather see a blocklist than greenlist. Person is being obnoxious -> person loses ability to post. It doesn't actually happen all that often that someone decides to be a jerk, and as such it is much easier for the GM(s) to deal with jerks than everyone who wishes to apply. 

As opposed to greenlisting...? How is a person supposed to express interest? PMing set as a part of approving process can and will turn people away. What if I want people to directly engage in IC (IC introductions)? [b]As few steps to let people start interacting should always be preferred over a more complex process, for the sake of the site's health.[/b] I am a member to several sites with similar approval systems, and it is nothing but pointlessly annoying. Barely anyone likes it.

In other words: please [b][i]don't [/b][/i]to greenlist-style approvals for anything besides PMs.