But that's a very different issue than privacy rights in general.
I would say this puts it a bit out of the comfort zone.
That's the problem with talking about a "right to privacy" in Anglo American law: there really isn't one. There are various protections serving different purposes, but they're not unified into some overarching principle of a right not to disclose or have information disclosed. That's why the subpoena power is so much broader than the power of police to search: because the animating principle isn't "privacy" but rather the protection of criminal defendants. If it were about privacy it wouldn't make sense to e.g. treat witnesses, who can be compelled to testify, differently than defendants, who can't.
Now, I'm not arguing that this is the best possible way to do things. But it's the way we have been doing it for centuries (since the Middle Ages).
As a general rule, there's "no money" in doing something like that. You run the risk of getting sanctioned, and if you use the information improperly in other litigation, it'll just get excluded as having been obtained via abuse of a subpoena.
The bigger worry is stuff like this, which doesn't happen under court supervision: http://www.wired.com/threatlevel/2012/08/administrative-subp....
http://en.wikipedia.org/wiki/Susan_Illston
> Sony v. Hotz
> Currently, Illston is the presiding judge in Sony Computer Entertainment America LLC v. George Hotz, et al.,[13] in which Sony claims that Hotz's jailbreaking of the Sony PlayStation 3 violates the Digital Millennium Copyright Act.
> She has granted Sony permission to track as much information as possible about those who had seen a private YouTube video about the jailbreak and to read their comments, plus obtain access to IP addresses, accounts, and other details of visitors to sites run by Geohot. The access granted by Illston extends even to those who had not downloaded the jailbreak code.
So clearly her interest in information privacy is non existant.