All right, it doesn't happen all the time. Some of the really great sitcoms have laugh-tracks to them (think Golden Girls or Just Shoot Me) but sitcoms are getting more and more guilty of using them to fill empty air time.
The original purpose of a laugh-track was to let viewers know when something was funny. Now, I know why government thinks we need the Electoral College instead of our votes doing the job directly but... jeez. People find different things funny and one thing people are capable of is knowing their sense of humor. Have you ever laughed because you heard canned laughter on TV? It hasn't worked for me yet.
So, not only do they not trust us to know when something is laugh-worthy but now we have bigger problems. What once was a cue for us becomes a harsh demand: We MUST find this funny. If the joke was relatively weak in the first place, it seems, they keep the track on longer...and longer...and longer...and, you guessed it, longer. Try watching a current sitcom featuring a laugh-track and take it out. Chances are, you will notice a lot of empty air between lines characters say. It not only gives false validation that dialogue is sharp and situations sparkling but also means the writers are writing LESS per script. **Three minutes of laugh-track boredom in an episode is three fewer minutes to write.
So, come on sitcom writers: Throw out your laugh-tracks, sharpen your pencils, order coffee, and laugh yourselves silly thinking up new things amongst yourselves. You won't need tinny chuckles to validate your cleverness and your audience will believe you actually find them capable of "getting" jokes on their own. If your audience can't find the joke, chances are it just isn't for mass-appeal. At least you tried then. You don't want to be another Carlos Mencia using thinly-veiled attacks on intelligence or blatant prompting to warrant a chuckle or approval for humorless slop.