I try to avoid giving people my number because then they'll start texting me. Inevitably. I'm a lot more tolerant of face-to-face conversation than conversation through text. And don't even get me started on Xbox Live chat.
Signatures, xD, numbers in place of words (2, 4, 1 , 8, etc.), exclamation points, CAPS LOCK, and simple messages that I can't respond to ("hey", "k", "lol", etc.) are all things that I can't stand when people text me.