I guess it was when I was working at Excite about ten years ago that I really started hearing people talk a lot about response time - how quickly you get the information you request on websites, how this can be optimized, why it's slow.
For my own part, I've been giving more thought to the question of personal response time. I actively hate talking on the phone (which is somewhat problematic in that I no longer live near the majority of my friends) so email is my main vehicle for communication. Sometimes I end up with a technology preference mismatch - I email, some of my friends are much more reachable by phone or text message - this can sometimes lead to big lags in correspondence (eg I don't really check my voicemail that often, other people don't check their email that often) Setting aside this medium mismatch, and while I realize that email is not IM, I'm amazed at the response lag time that some people seem to think is acceptable.
I've been trying to monitor my own behavior so as not to be one of those slow responders. Slow response is particularly annoying when trying to make plans - eg how long are you supposed to keep times available after you offer them up? If you continue to follow up it can feel somewhere between harassment and chastisement for poor email etiquette. If you don't follow up you can be left to wonder whether the original email was received or if it ended up in a spam filter (only for those poor souls using a non-Postini spam solution). But exactly when did it become socially acceptable not to reply to invitations?
Personally, I think my worst response time comes with the most personal sort of emails - as the type of exchanges that for many friends are hour long phone conversations, for me often end up in my email queue (per my distaste for the phone). Sometimes I just don't have the emotional wherewithal to have the kind of reply that the email warrants even when I have the best of intentions and the highest esteem for the sender.
I read a book several years ago called Memos from the Chairman, written by Ace Greenberg, then CEO of Bear Stearns. I remember generally enjoying the book, but the item that most stuck with me was that he made it his goal to always respond to inbound correspondence within 24 hours (or at least that's how I recall that part of the book.) Sometimes the response was simply that he had gotten the message, didn't have time at the moment to address it but would get a full reply as soon as he had time. Still, that counts at least as an acknowledgment. The book was written before the ubiquitous nature of today's email, so I'd guess he had fewer inbound requests than his successor does today, but he was the CEO of Bear Stearns. If he could get back to people within 24 hours, it's hard to think of many people who can't. I know lots of people who think that they're too important or busy for fast response times, but my own observation is that some of the busiest people I know are the fastest to respond. Sometimes these responses are even incredibly long and thoughtful replies.
I think it comes down to the kind of style that people have chosen to adopt. It seems that the fast responders basically have a FIFO approach to email management - they read an email, they deal with it, it's done. I am aspiring to be one of these people. The approach I have followed too often is the one I see too many other people following as well - essentially random - read an email, sometimes respond instantly, sometimes plan to respond to it at a later point (maybe more information needs to be gathered, a schedule consulted or more time needs to be allotted for the reply than is currently available). Maybe I get back to it or maybe it gets lost in the queue of forgotten emails. Since I've switched to Gmail, even more emails fall off my radar as only 25 emails are in view on my front page.
I'm really trying to reform, and hope others will as well, as I think Ace had it right. So anyone who hasn't replied to my emails lately, get on it :)