Today, the not-arduino tag was added to a bunch of questions. Apparently it is for questions which do not want an Arduino solution.
Is it really necessary? If someone doesn't want to answer arduino questions, they can just ignore the arduino tag (the 'ignore' functionality makes the posts disappear).
The reason meta-tags are a problem is that they do not describe the content of the question. They describe some other aspect of the question, like the author’s skill level, or the author’s motivation for asking it, or generally what “kind” of question it is (poll, how-to, etc.).
Meta-tags are actually a subset of a larger problem that I usually call dependent tags. These are tags that don’t say anything by themselves – you can’t tell what the question is about unless they’re paired with some other tag (or several of them).
It seems like a dependent tag to me. It is also pretty similar to "author's skill level", in the sense that it is filtering out answers based on what the author will and won't accept; whereas other people/visitors may (after all, we write answers for visitors to read, not just to help the OP).