One line of argument that really bugs me is when people say that a group in question is the "last acceptable target" for jokes. Most recently, someone claimed that poor white people were the last acceptable targets. I provided some alternate targets, and those targets "weren't the same" for reasons relating to Jeff Foxworthy's success in the mid nineties* and unrelated to his obscurity since.
One wonders if, in an ideal world, one would even have acceptable targets. As far as targets relating to race and culture go, we ideally probably shouldn't. At the same time, I don't particularly have a problem with having some cultural standards, though at times that leads us to cut some pretty fine distinctions. (I was telling theCSO yesterday that I don't judge "Bombshell" McGee because she dresses skankily, I judge her because she ACTS skankily, and yes, I judge Jesse James for the same thing.)
Anyway, TVtropes.com has made my day by compiling a list of acceptable targets of various varieties. Some of them might not be acceptable among your friends, but the site generally provides enough examples that I'm persuaded that people meeting that description are to some degree targeted. Also, there are plenty of groups (people with dwarfism come to mind) that my friends wouldn't tolerate snark about, but that I totally see are comically fetishized by the larger culture.
Acceptable Cultural Targets
Acceptable Ethnic Targets
Acceptable Hard Luck Targets
Acceptable Inevitable Targets
Acceptable Lifestyle Targets
Acceptable Hobby Targets
Acceptable Nationality Targets
Acceptable political targets
Acceptable Professional Targets
Acceptable Religious Targets
Acceptable Sexual Targets
I suspect that each of those lists contain at least one group I think my circle of friends would find it acceptable to make fun of and one group that I wouldn't. (E.g. I think I can safely say that for most of the people I hang out with, making jokes about Mexicans is not acceptable, making jokes about Canadians is. Similarly, making jokes about transsexuals is not ok, making jokes about furries is. Making fun of Mormons, not cool, making fun of scientologists, ok.) One could argue that part of the difference is that different sorts of jokes are made about Canadians and Mexicans, given that Canadians are usually mocked for their politeness in a way that half comes off as the joke-teller mocking America by implication. That distinction breaks down with the second example, though.
Anyway, no one group should ever consider itself the "last acceptable target."
*Any kid who grew up about when I did knows that about the time Jeff Foxworthy became famous for insulting poor whites, the least cool rich black guy of them all, Carlton Banks from Fresh Prince of Bel Air, was going off the air. Many people who were teenagers of the early 1990s can still rap the theme song. Some sociology student has quite the dissertation topic right there.