My suggestion is to mandatory have to include a tag wich has either 50+ questions (or better 100+ questions, my preference). I think this demand is reasonable.
Why do I want this? All the time in tag
interesting questions, questions comes up with only one tag, and that tag is a very rare tag.
I'd like filter those out, not really possible. (I have made a filter for questions with something of 500 keywords). This category of questions also involves tags wich simply is a synonym for a much more common tag i.e. webkit.net (26 questions) instead of webkit (3000+ questions).
Examples of recent questions I've encountered with these rare tags are this (1), this (2) and this (3).
Extra tags needed in these cases are.
(1) "p2p", (2) "database", (3) "angstrom-linux".