Twitter Offers Metered Pricing for Firehose of Tweets

Because they would be (rightfully) accused of attacking their own ecosystem. Because people (rightfully?) believe that they should focus on their core product first and not dabble in somewhat related areas until that is stable. Cf. the backlash when they brought out their "official" apps.

They, like every other community site, have a ToS that grants them rights to publish and sublicense user submitted content. They couldn't function without it, when you view a twitter feed with your browser and see sponsored trending topics, they're "selling" content:

> You retain your rights to any Content you submit, post or display on or through the Services. By submitting, posting or displaying Content on or through the Services, you grant us a worldwide, non-exclusive, royalty-free license (with the right to sublicense) to use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute such Content in any and all media or distribution methods (now known or later developed).

http://twitter.com/tos

If you had just spent $3 million on a super bowl commercial, how much would it be worth to you to know the immediate response to that commercial when it airs?

Can't work out a lot from the site, what sort of services are you providing as part of the alpha? Is it API access?