There are few people now who wouldn't understand what you meant if you said "Joe Jablonski? Yeah, I know him...well, I don't know-know him, like, face to face. I internet-know him."
And there are whole nuanced tiers to internet-knowing someone...
- You recognize their name because they run in the same circles you do online. Further, people you know and trust have mentioned them, and never with negative connotations. This is like the baseline level.
- You recognize their name because they run in the same circles you do online. Also, you read their stuff every now and again, and maybe even been in the same conversations or message threads, but never directly interacted.
- You find yourself in the same discussions and directly interact on a reasonably regular basis.
- You find yourself in the same discussions and directly interact on a reasonably regular basis. Further, you have exchanged the occasional PM/DM/emails regarding the topics of those conversations.
- You find yourself in the same discussions and directly interact on a reasonably regular basis. Further, you have exchanged the occasional PM/DM/emails for purely off-topic, social reasons.
- You talk on the phone or Skype/Google Hangout/FaceTime at least semi regularly.
- You've hung out in person, at which point they have earned the "IRL" designator and are no longer an imaginary person who lives in your cell phone and computer