I noticed just now from the answer by RegDwight to this question that the tags are pluralised.
However we have meaning and not meanings, word-choice instead of word-choices and so on. (Even the 'official' discussion instead of discussions for meta.)
Shall we decided to use, in general, the plural or singular form for tags? (Incidentally, we have tags instead of tag but this should definitely not be seen as an exception, since the discussion is about all tags and not just one of them ;).)