This must work! Make people enter status messages. If you leave a status more people will instant message/reply back to you. When people message you back you feel great about yourself and you want to use the service more.
Lets take a look at all the different services and what they use to make you leave a status message:
AOL Instant Messenger (Old):
A simple “Set Status Here” works. I like Twitter and Facebook’s direct approach on asking a question for them to answer.