When people start a conversation with me but then expect me to carry it on.
People do that all the time online.
Them: "Hey."
Me: "hiya"
Total absolute silence.
The funniest thing is when that's been your entire conversation and like 3-5 hrs later suddenly you get a message like...
"afk, I gotta go walk my dog" or like "brb" or something... it's just like LOL what!