In other words, it's jargon from a specialized or small group of people, and it can annoy other people when you use it too much or when it seems to be used to exclude people. Abbreviations can be similarly annoying.

L8R!

In this situation I am using the British definition of the word "torch" since the traditional French Christmas carol is not "Une Lampe de Poche, Jeanette Isabelle."

Jeanette Isabelle

"Leet" speak derived early on when the Internet was a series of bulletin boards. Hackers learned that their "secret hiding places" could be found with simple word searches of boards. So "leet" (short for elite) speak was invented. 1337 is leet. Haxxor is hacker. pwn is own, as in "I owned him in that game (I bet him senseless)". By misspelling and by substitution, the guys who hacked into games and such could remain hidden from the searchers. As time went on, the "leet" became more of a derisive than an accomplishment. Now, only true losers use it to any extent.

And let's talk spell check. Usually useless. How many TV news crawls have words spelled wrong? Or words that are correct in spelling, but it's a sound alike - oar and or for example. Makes me crazy.