Two things: we've only heard about a "subpoena," not a "Grand Jury Subpoena."
And we've heard that Mark Karpeles is the CEO of "Bitcoin". I wouldn't read too much into the exact phrasing of the news media.
Here, it sounds like MK or Gox got served with a regular subpoena (but I guess we don't really know).
I'd say we don't even know if it's really a subpoena. The news quite often get terminology like this wrong.
If that's the case, I think my initial point still stands - either there are charges or its for somebody's else case.
Your point which I disagreed with was that there have to be charges (or a civil case) before there's a subpoena.
You didn't say "regular subpoena" (if you had, I might have asked what you meant by a "regular subpoena"). A grand jury subpoena is a subpoena. So is an administrative subpoena, for that matter.