How do I know thee? Let me count the ways.

Prompted by a conversation on Twitter that went something like this (details removed so we don't have to discuss the actual issue itself)

Journalist - Link
Journalist - Joking/sarcastic comment about link
Me - Another sarcastic comment

Journalist - I was being sarcastic! Don't believe I think that.
Another human being (who I assume doesn't know the journalist personally) - I was worried for a second.
Me - I was joining in with the sarcasm - I didnt think you meant it!
Journalist - Phew!

I realised that I had assumed that the journalist knew that I "knew" her well enough to know that she would never say anything like that seriously. Which is of course madness. She doesn't know me, I don't know her, neither of us knows the third person, and yet I assumed that she would know I was being sarcastic, and she cared when she thought that we had misunderstood her joke.

When you communicate with people online, do you feel that you know them? In the online world I can feel that I know a lot about people's opinions without knowing very much about their lives at all. Age, location, marital status, children, even sex in some cases. All of these are secondary to what someone thinks about a new TV series or the best way to mix a cocktail or whether crocs are the work of the devil or comfy enough to override the ugliness.

In real life the opposite is true, when you meet someone the first things you find out about them are the externalities, the house/job/children, but in order to get to know someone, to know if this is someone you want to meet again, you need to chat about what you think about things, not what you have or what you do but how you feel about issues.

I can't see any way to change this, however, without sounding like a deranged quizmaster.
Nice to meet you, now what do you think about MSG? Which is more important, a good haircut or good shoes? Which Beatle do you like best and why?
I can't see it going down well.