You know when you're talking to someone and during the conversation you'll mention something, and the person goes "Oh yeh" and you get the distinct feeling that they don't know what you're on about, but are pretending they do?
It's been happening quite a lot lately and I end up blurting out "are you sure you know what i'm talking about".
And of course, this is followed by the customary reply of "Oh yeh, yeh, honestly I know what you mean", before trying to change the subject. Then you know they're lying. It's a hilarious textbook example of how most people would rather feign knowledge than admit ignorance.
Not being patronising, it's just happened twice to me today and I decided to verbalise it, although admittedly a bit of a random post.