I'd like to point to:
http://en.wikipedia.org/wiki/Wikipedia:What_is_a_troll
http://en.wikipedia.org/wiki/Wikipedia:Trolling_poll
The first is an impressive piece of work by User:Snowspinner and others on how we might define trolling. The second is a poll on the definition and on a potential policy based on it.
My own view is that allowing admins to block on the basis of "trolling" is very risky. It is too subjective and open for abuse, the current policy of allowing blocks for "simple vandalism" is already problematic enough.
I would support the policy if enforced by the Arbitration Committee however - that would increase the safety, both by slowing down the process (sometimes too much maybe, but that's better than instant bans in my view) and by making the decision a group one rather than by a single administrator.
My other concern is directed at Jimbo. Until now banning policy has basically be set by him, and I wonder about the validity of any major policy change in this area set by poll. I'd be interested to know - if this is agreed, would it be a valid policy?
Regards
sannse