I think things are funnier to me when there's someone to laugh with. Especially when it's at a time we aren't supposed to laugh. And I think it's worse when it's with a family member or close friend who has thought patterns similar to mine. In those cases, we often don't even have to say a word, and still both find it funny.
Case in point... When I was a teenager (probably about 14), my mom and I were in a doctor's office. This other kid, about my age, came in with his family, and he was carrying a clear plastic bag. In later discussion, we found out we were both wondering, "What's that bag for?" And I guess you know sometimes your eyes gravitate toward something that's insignificant, but your curiosity gets the best of you and you stare at it without even thinking... Well, I found myself staring at this guy's plastic bag. Shortly, I found out what it was for...
[spoiler]This kid starts puking into his bag. And we lose it. I had to go outside to get control of myself. We know someone being sick isn't funny, we both felt sorry for the kid, and we couldn't have blamed his parents if they'd have been really ticked off. But I guess the situation, wondering what in the world that bag was for and then finding out in the manner we did, in an environment where it wasn't appropriate to laugh, was too much.[/spoiler]
Some of y'all probably think I'm awful now.
But it was one of those things.
And about the canned laughter... It's probably a good thing, even if it does seem silly. The experts do say that it's good for your health to laugh.