The problem with meta tags was that they were often misused.
[beginner] was one of the worst - many users would tag another person's question as
[beginner], which is wrong. Some people may see this retagging as an assessment of their ability based on the question they asked, and might take offense. It's also subjective, what's beginner to some people is intermediate or advanced to others. Who gets to decide?
Even worse was the
[subjective] tag. Users would come here and complain that their posts were closed, even though they added the
[subjective] tag. Arguments would occur in question comments for the same reason. The point is, subjective questions aren't allowed on Stack Overflow, using this tag as an "escape clause" was just annoying.
Yes, some meta tags were kind of useful. FWIW, I liked the
[best-practices] one, although I think that's because when it was here I was one tag closer to the generalist badge. ;-)
I can't see meta tags coming back. However, some meta tags will stay under the radar - Jeff said himself that he's not going to specifically look for meta tags to ban. I do wonder if some meta tags should be allowed, perhaps in a different style (like the moderator-only tags here), and you couldn't earn badges on them.