On the other side you've got the people who think the Firehose is the greatest thing since sliced bread and is pretty much a golden ticket.
I don't think I get Twitter - I've never found the service to be at all useful, and I find the 140-char limit quaint and out of touch with how users want to use the service (see: URL shorteners, tweet expanders, Twitter-speak shorthand, etc). However, I am willing to accept that there's a social network I totally don't get that nevertheless rakes in some serious money (like WoW!)
But what exactly is the value of Twitter's data? Unlike Facebook, Twitter doesn't even remotely approach having a representative sample of the population. My parents are on Facebook, my uncles and aunts are on Facebook, along with everyone from my generation - Facebook has meaningful demographic data. What data does Twitter have that isn't almost exclusively limited to "young, urban, tech-savvy"?
As a marketer or data miner, what is so good about Twitter's data that would compel me to pay The Big Bucks(tm) for such a feed? Maybe I'm missing something, but it seems like Twitter's biggest proponents believe that the company can justify a multi-billion dollar valuation by providing glimpses into the thoughts of a tiny sliver of the population at large.