I've been seeing quite a few questions in the process of being closed as unclear what you're asking, apparently because they don't specify an OS. I've also been voting to close these questions. My question, though: should we be?
No, if OS isn't given, we can assume that they don't care.
For two reasons:
A lot of people have access to multiple OSes. Its not unusual to see people (espically power users) who use Linux, windows and Mac.
Alot of software now, will run on all OS's, because the OS market is diverging. We've seen in the last 12-18 months Games, which used to be a big hold out for only working on windows are now becoming very common to work on linux as well. (and we can credit that to Steam and Humble Bundle).
Also it looks like the Tags are not nesc the way we refer to OS. See: Tag for OS-agnostic questions?
In my opinion, it is a bit overdone to aggressively close these question. Ask in a comment if the asker can edit in his preferred OS in the question, and if it is done, delete your comment (and flag the response as obsolete). This prevents potentially good questions to be overlooked, and I can not imagine that an asker will not add the necessary information after such a comment.