How many people do you follow on Twitter? I manage an account that follows a few thousand (I use DMs for content submission), and I have to wade through so many useless DMs.
I agree with Tichy, reading this unfortunately made me disinterested.
I will say though, the design of the site is nice. I especially liked the footer graphic, which was a cute touch to the Twitter bird, if a bit cliched.
That being said, we're definitely interested and proactively working on ways to provide value for users of our service and those that receive messages. I would say about 50% of the campaigns are sent via DM and the rest just to the public timeline. Our most valuable clients tend to use the one which makes the most sense to them.
We do have a few users that just spam their followers (per our definition of spam) and the updates listed in the other post will hopefully curb them off the site. Additional ideas would be great too.
I'd love to see Twitter provide more granular control over direct messaging and allowing you to follow a user but not accept DMs from them.
Thanks for the constructive criticism!