You know what might just be the most annoying conversation pattern ever? People who interrupt you while you're speaking and then ask you the question you were already trying to answer. Things like this (a made-up example):
They: So, can you ride your Segway on the streets?
Me: In Washington you can, but it only goes—
They: Uh-huh, okay. How fast does it go?
Me: It only goes 12 miles an hour.
They: Uh-huh, okay.
Conversations with these people are so bewildering. At least they're always short.