I'm afraid I must provide an alternate
point of view:
How are people supposed to get to know each other without a "first contact", so to speak? What if you didn't shun these people, and you someday met someone who is intelligent, has common interests with you, and is not "desperate"? You already are a UNIX user, and the person messaging you probably is as well, so they are probably at *least* somewhat intelligent.
Not everyone who seeks out communication online is "desperate". Sometimes people are just shy and don't want to confront someone in real life that they don't already know something about. These people can end up being interesting to talk to once you get to know them. I personally have met the vast majority of my friends online and they are all meaningful friendships.
If you have an interesting .plan and .project, and leave messages on, it is cruel for you to blow people off who just simply want someone interesting to talk to. Give them a chance, and if they prove to be a**holes, then tell them to go away. If you don't have time to talk to someone, just...
It's that easy, and you won't be perceived as a jerk