Twitter: Responsible for Content?

As I read GigaOM's Is Twitter a newspaper, or is it the phone company? today, I began to ponder the question. For those not familiar with the story, GigaOM is referencing a WSJ blog, which is in turn referencing The Age. The long and short is that Twitter is being sued for defamation.

I was immediately reminded that just a few weeks ago Twitter CEO Dick Costolo told AllThingsD Twitter is in the media business, but is not a media company.

In the United States, the Communications Decency Act ("CDA") (47 U.S.C. ยง 230) dealt with this for AOL (and other forums) by proclaiming "No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider." Here, I would expect that Twitter would hide behind CDA, asserting that in so much as it filters content, it does so as a "good samaritan." But is this really the case? When twitter builds aggregated feeds, or includes paid tweets (perhaps even written by Twitter's advertising team), does it become a content provider? When Twitter rewrites a link to use their URL shortener, are they a publisher? In fact, the mention of ads reminds me of the Google prescription drug ad case.

We'll see if Twitter manages to walk this line successfully, or if their practices must change. I'd generally prefer to see them alter (and filter) content less, and allow users to make good decisions. Then again, filtering URLs for malware has societal value.