The analogy doesn't really make sense to me. Twitter isn't a news service, it's a communications platform, and Twitter users aren't necessarily politicians.
The analogy holds because Twitter is 1:N, not 1:1. They are publishing information to a large amount of people that people use to educate and inform themselves.
And I already stated that doing this for every Twitter user is slimy. But retaining the record of how a politician has communicated with the public? That's in the public interest.