So, as a public service, I'm going to talk here about some cardinal principles of satire, in the hopes that someone who tries to write it will take heed. These are the most important things to keep in mind when one tries to write satire.
One: Satire's first, oldest, and best target is hypocrisy--particularly the hypocrisy of the rich and/or powerful. It was true for Jonathan Swift, it's true for The Onion, it'll be true for tomorrow's great satirist. When one writes satire, one should go straightaway at the double-standards of what's being satirized.
(Note that some would consider vanity or pretense, not hypocrisy, to be the best target of satire. However, pretense is itself a form of vanity, seeing as how it's an attempt to make you look better than you really are in the eyes of the world. And all vanity has a tasty hypocritical center--remember that "hypocritical" means "under-critical;" in other words, you don't criticize yourself by the same standard that you hold the rest of the world to. In the case of vanity, you insist upon your own appearance as a mode of perfection, while denigrating the appearance of others for failing to live up to your standard.)
Two: Satire always plays it straight. Satire is always deadpan. Satire always wears a poker face, never giving itself away. I'm going to repeat that, with emphasis. Satire NEVER gives itself away. At its best (and this is what I think Jon Stewart is really good at), satire is the straight man, holding back and letting its targets have enough hypocritical rope to hang themselves. But you can't do that if you're holding up a big sign saying "NOTE: THIS IS SATIRE".
Three: Following on from the previous point, it's important to remember that satire is not necessarily humorous. In writing satire, it's often tempting to turn to the audience and tip a sly wink to them, to say "Oh, don't worry, I'm not serious, I'm just having some fun." Satire, however, is always as serious as the grave-- or as serious as eating babies, if you prefer. You may often find laughs in satire-- but if a laugh is there, it is almost always there to cover up a scream of rage. Satirists themselves are just optimists who've been kicked in the nuts by life a few times too many. (And if you think that's too glib, read about the life of Jonathan Swift sometime.)
Satire isn't driven by "let's have some laughs;" rather, it's driven by "I'm mad as hell, and I can't take it any more."