Like others have pointed out - different forms of humour are acceptable. It all just comes down to the timing and the audience.
Some people might find humour in jokes about death, however, those same people may not like those particular jokes at a funeral.

It all boils down to; context, timing and the audience.

depends on audience, I agree. Personally I dont care. Its the internet, does it matter?

Someone that makes a joke soon after a big tragedy will be labeled as insensitive. Someone who keeps making racist jokes over and over eventually will be labeled as racist. If you make a joke targered to insult someone,that person will still most likely fell insulted being that made for other people laugh or not. It really depends on when you use the jokes and how you used.

Humor has a way of breaking down barriers, true.  But humor if done in certain similarly minded groupings can actually strengthen hateful concepts.  It really depends on the mind and values of the comedian.  The phrase, "You should never take yourself too seriously" is true, however sometimes seriousness comes from making light of issues important to others.  There is no exact right or wrong in this.  You cannot assume humor is good or humor is bad anymore than you can consider people or groups of people fully good or bad.  This is a misconception. 

Granted, we should have a very broad sense of humor and challenge ourselves to see every other point of view.  Humor at it's core is good for our system functions and potential happiness.  But imagine you joke, making light of someones problems, they kill themselves, and then you feel guilty for the rest of your life.  You could argue that that was their problem instead of yours, which in part may be true, but humor is powerful communication with the ability to persuade based on loose understandings without logical basis.  As communication, you should always consider those with ears, despite how minority they may be.  Majority has been responsible for wars, holocausts, and more.  It has a way of drowning out the minority or ignoring them toward the majority goals, just as humor may. In a way, humor can be considered the voice of the majority.  While Majority may feel correct and validated, feelings are not always an ethical source of information or an ideal reason to initiate an action, ask any murderer or criminal.  Also in the end, was that humor good for you?  For them?  No, humor is not always justified, because society does not always provide justice. Topic though?  Same grey area.  With great power comes great responsibility, but topic itself should not be a restrictive element.

Oh yeah, I guess that is true as well. Sometimes jokes are made to insult people, and that makes things a bit more complicated.

No.

Only bad jokes...

I sincerely believe no topic should be off-limits when it comes to using humor. I think it's how the topic is dealt with that matters as well as the context. There will always be people offended no matter what the topic is and deciding that one topic is ok while another is not is a form of censorship.

I think good humor is ok if one can tell that it's just humor and not a hidden message of some kind. I'll take two artists in example whose humor is excellent but out of context some stuff they say could cause trouble...

Louis C.K. and George Carlin.

Abortions are on of my favorite topics of humor. Though an Abortion Humor thread would probably be terminated before it even got a chance to live.

where do you stop the censorship; and who decides?