For of few of the lesser known acronyms...

FUBAR Fouled Up Beyond All Repair (substitute more colorful term for Fouled up as required)

AFAIK (I think this is what Steve intended) As Far As I Know

ROFLMAO Rolling On Floor Laughing My A$$ Off

TTYL Talk To You Later

I agree with the idea that email should avoid jargon, TLAs and anything else that makes it less readable subject, in part, to the intended audience. If the audience is known to understand, it is less of an issue. Still how may cases of carpal tunnel syndrome will by causes by typing 'You' instead of 'U'. To me, especially in email or a forum where you have virtually unlimited space, that is simply lazy.

What is even worse, in my opinion, is the generally poor quality of spell checkers. That or they are not enabled. When one is translating from one's native language to a second or third language, that is one thing. Mistakes or errors in usage are expected. But if you profess a language to be your native one, try to use it correctly. And if you need help, there are a bazillion spelling and grammar checkers available to help you.

I once worked with an IBM Sales Engineer who was doing a presentation on what was then a new technology, SNA. In the beginning of his presentation he showed a Tower of Babel covered with numerous acronyms from IBM. He noted the subject of the presentation, looked at his own display, then commented dryly that 'at IBM we have to many TLAs'.