Being able to phrase pithily is a skill but in the end it's just schtick. Things are funny when you don't expect them, and/or they create a fresh insight.

A really rare skill these days is being a listener!

...occasion, occasion, occasion.

I agree with you. I have noticed that it is some people's "thing" to wait for someone to be vulnerable or make an insignificant mistake so that they can then swoop in a crack a joke or be condescending at the other person's expense. I find it really lame actually because I too have noticed that these are often people who dont do anything or have anything to say, then try to build themselves up on the backs of others. It's very parasitic in my opinion. They always leave a way out for themselves too by claiming "its only a joke" or "oh relax, learn to take a joke" when you call them on it. It's like, ok we're all friends here and its nice to spend time together and all this person can do is wait for an oppertunity to 1up some friend of thiers in front of everyone else.... and then you also aren't allowed to call them out on it?! If that is what hanging out or being together is all about, leave me out of it. I'd rather build people up instead of cutting them down.