When someone makes an attempt at a JOKE... No, unless I actually find it funny. My friends know I'm a big stand-up comedy buff so I usually respond with a quip of my own. But I won't be a complete douche and tell them it wasn't funny or anything.
However, if someone tells me a STORY about something that happened to them that's supposed to have a "funny" conclusion and I DON'T find it funny... Yeah, I'll faux laugh. I went through a semi-depressed, overly cynical phase a few years ago which I know pissed off most of my friends, so now I try my best to be upbeat. It actually helps me too, I've found. So no, I have no trouble "playing along".