I've recently come across an article by Adrian Magson in Writers' Magazine with the rather ambiguous title of "Spell it Out". "Make sure readers know exactly what you are talking about," says he.
OMG (= Oh my God) that's so true it isn't even funny. I mean, using acronyms in twitter may be a useful way to fit the word limit, but anywhere else (and sometimes there, too) it's worth the time spent on explaining what you mean. Not everybody is up on the lingo, so to speak. You can't expect your readers to know everything, especially if you're aiming to market your book internationally. What a reader from the US understands without question doesn't necessarily hold any meaning for someone from Spain, or Greece, or Russia. Or worse, it might mean something completely different. That holds true on other levels, but let's stick with acronyms for now.
Here's a couple I use that are probably understandable:
I think I'd feel safe enough using any of those in a story, should it fit the context, but mostly I'd do as Mr Magson advises and make sure the reader knows what I'm talking about.
What do you use regularly and have you come across any strange ones that you had to look up? How much explaining do you think one should do when writing, and how much can you just imply and trust the reader will understand?
ps. spot the acronym I smuggled into the list... *grins*