person1: blah blah blah blah blah blah...
This is undoubtedly how most of your IM conversations start. But why? Why the initial hey? Just say "Hey, blah blah blah blah..." Why do you need for me to acknowledge your initial "hey" before you tell me what you're going to tell me?
IM isn't a phone conversation, it's a text message. When you text someone, you don't have to preface it with "hey" and then wait for a response. Just say what you're going to say and let the person on the other end decide what to do with that information. Maybe they will respond, maybe they will not. If it is really important, send an email.
And don't get me started about people who ask "did you get my text?" The answer is always "Yes, but because i'm an a-hole, i never bothered to respond."