IM is encroaching on our privacy.
One of the first, and greatest, instant-messengers: ICQ, would literally reflect each letter as the other user typed it.
Modern IM clients have that feature removed, and I think with good reason. It was an embarrassing, distracting, sham, to watch someone type and untype and rethink their statement, making typos, etc. The feature encroached too closely upon our personal space concerning exactly what we were doing with our computer at every single moment.
I know that services like Facebook and Twitter have encouraged people to share more and more about exactly what they are doing at every freaking moment of their boring lives, but there IS a limit. (Most) People would recoil at the idea of having all their computer usage screencasted onto the web for everyone to see what they were doing at every single moment.
I've noticed a privacy-encroachment creep in the feature set of IM clients lately. First, they wanted to tell other people whether I was idle or not (uh no? then i have to actually respond...). Then they wanted to start informing the other person of when I am "typing"! This brings us much closer to the original ICQ faux-pas...it's not quite as bad because they can't see my every typo, but they know when I'm "typing" to them. I say "typing" in quotes, because if I type a few letters and then let the cursor hang and blink on the textfield, it'll consider that as typing...even if i've gotten up to say, brush my teeth! What a piece of crap.
Ok, finally. The last straw. My Adium client, thru Gmail, reports me as "leaving" or "entering" the conversation based on whether I have the IM window open! So now someone knows if I've closed the window! It becomes a subtle point of etiquette not to close the window, even tho sometimes what the hell I've got nothing to say and I've read everything the other person has to say...come...on...
I want off the privacy-loss-train. You can't know when I've closed your window, or how long it takes me to ponder my response to your dumb-ass comments. You can't know that I'm idle (i'm supposed to be "working from home!"). You can't know when I'm watching porn, or that old britney spears music video...that's just for me and my history-menu.