It is not surprising that something which is broadcast publicly is public.

It is very, very surprising that the public nature of anonymously-published material is in any way relevant to whether the private identity of the author should be disclosed.

The subpoena was based on rules that assume that the twitter user's email address and direct messages (like public tweets) are already public. This is surprising since I think most Twitter users would agree that those things aren't expected to be public.

I think you are confusing personal identifiable information with direct messages. The direct messages _do_ have an expectation of privacy around them, but that information was never requested.

https://www.eff.org/sites/default/files/destructuremal%20Sub...

The tweeters in Tahrir square however would have got killed had they screamed out of a window. Twitter gave them a public forum and anonimity. A completely novel concept, and one that deserves a more careful ruling than this brash analogy.

It's the same simpleton internet to real world translation the MPA/RIAA use to equate "file sharing" to physical theft. It's an easy analogy to pull the wool over the eyes of less technically inclined individuals.