2. Transmitting an unintended message by accidentally pressing the space bar.
3. Insulting your friend with an unintentional response to their status update because you didn't realize facebook changed the format for entering text without the need to press the "enter" button. And to make a new paragraph, you have to hold the shift key + space.
I prematurely tabulated when responding to my friend's facebook status by typing what I would really like to say but shouldn't and transmitted the unintended message by accidentally bumping the space bar. I dislike premature tabulation!