I agree that the number of posts doesn't really matter (after all, someone who has posted 15 confirmed reports on HeroesWorld already has at least 15 posts :) ). I also agree that the composition of the Arbitration Committee (AC) should be decided by those who play Heroes 3 (primarily, online) and that tournament organizers should also participate (for example, Ketch). Moreover, those who play on HeroesWorld — since the AC resolves disputes concerning online games of Heroes 3 on HeroesWorld and does not automatically review games on, say, Bay (unless invited, of course ;) ).

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Users of HeroesWorld who have played in at least one online tournament of Heroes 3 on any resource in 2009-2010 and who registered on HeroesWorld no later than last year may participate in the elections; as well as all HeroesWorld users who are organizers of Heroes 3 tournaments on any resource.
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Based on the principles:
1 restrictive — the composition of the AC voters should include only those whom it concerns.
2 expansive — the composition of the AC voters should include all those whom it concerns.
I'll slightly polish Kash's proposal (to account for the opinion of those who play seasonal games a lot but, for one reason or another, have not participated in any tournament), also replacing specific years for universality:

Users of HeroesWorld who have been registered for at least 3 months at the time the voting begins and, additionally, meet one of the conditions described below may participate in the AC elections:
1. Participation (without being disqualified from the tournament) in at least one online tournament of Heroes 3 on HeroesWorld, or
2. Having at least 15 confirmed reports of Heroes 3 online or their confirmations on HeroesWorld, or
3. Organizing and conducting (until full completion) of at least one Heroes 3 tournament on HeroesWorld (whether offline or online).

P.S. 2 Spirit — if there are similar attempts at cloning posts, don't count such fake players in the voting (and without warning them in advance, let them try, why not :) ). I think the principle of democracy won't suffer from this, and I didn't want to clutter the criteria because of such possible loophole-seeking...