One of the recurring, yet subtle, responses to the initial post is "you're just an old-school marketer who doesn't get it..." - which, as a dyed-in-the-wool direct marketer, seems similar to saying "neener, neener, you're a wiener." It's a strategy that wasn't all that clever in grade school and does nothing to help advance the cause. As a marketer, I "get" what drives cost-effective revenue to my company. If the value of Twitter is undetermined, just say so! It's a lot better to position it as a tool of experimentation rather than an unknown "next wave."
The other strain of response is that Twitter is a listening device. Not to sound totally crass, but so what? Businesses have (at least in their minds) done just fine without leading-edge listening devices. What's the value of listening to your customers? If it's so great, then why are the research people shoved so far in the back of most companies' marketing departments?
The third line of response is that "it's new...", which is kind of funny when you consider that most social media decks talk about the amazing speed with which social media has been adapted. Kind of like having it both ways. You're right - it is new. And the face of these communications will probably change dramatically in the next 12 months.
To sum it all up, the jury is still out on Twitter. Way, way out in terms of effectiveness as a marketing vehicle. There are some successes, but they're small. People point to Dell and Jet Blue, with good reason - they seem to have Twitter programs that generate revenue. What both of those programs have in common is the releasing of cheap inventory...so itseems that Twitter does have a marketing use for unloading distressed inventory at the last minute.
It looks like the problem with Twitter is in positioning. People keep talking about it like it's the be all and end all of marketing. It's not. It's a tool. A small one, as compared to all the other existing marketing channels. One to keep an eye on...but one that - if you're not in the right position to make it work (cheap, last minute inventory and/or interesting news), will end up causing you to waste a tremendous amount of time.
Don't let your senior management bulldoze you into investing more in Twitter than you should...Twitter is like a 5 year old who can hit a golf ball really well. It might turn into the next Tiger Woods...but it's unlikely.