I don't post to Twitter all that often, but when I'm going to be at the computer for a while I will often open the timeline for people I'm following (either via the web or Twhirl) and see what people are chatting about. I looked at it in depth a few months ago as a possibility for ad-hoc chatter among my geographically distributed team (we ultimately decided to use Campfire instead). Since then, I've had occasional exchanges with people and posted the odd update to my feed.
As of this post, Twitter's down... again... it's pretty amazing that a business with this much buzz and hype around it has allowed itself to become so unstable.
The stories of its frequent downtime, complaints about scalability, and departures of technical staff are regularly cruising through my newsreader. There's even a site that tracks the various "We're down" images that they use when the site is unavailable (the one at right is from the current outage).
I can't imagine what the behind-the-scenes issues are or what sort of challenges their tech team is dealing with... but clearly there's a problem here that they need to resolve QUICKLY. You have to assume that, at some point, people will decide they've had enough and move on to alternatives like Pownce or Jaiku. Or, as Scott Hanselman suggests in this post, maybe an open and standards-based alternative pops up to fill the void.
Lots of people are looking to Twitter as an omnipresent option for quick communication of status info, marketing messages, news delivery, and as an entry point for simple API messages. Most businesses and web properties would kill for that sort of interest and traffic... to have all that opportunity pass by because of stability issues would be such a waste.
On the other hand, imagine the case studies (for both Business and CompSci)...