Phillip has a point with the multisig--the less people needed to sign off on a transaction, the better odds that a few people go rogue and take the funds. We need to be careful in choosing who holds keys.
You know what though--you're right. Doing this "informally" works totally fine, right up until something goes wrong. I wouldn't want this to spiral out of control.
If we were to form an actual cooperative, AFAIK members would have equal rights in voting regardless of investment. That probably won't work, because people with the largest shares will be underrepresented.
Now, my knowledge of corporations/cooperatives in Canada is limited, but I'm certain we'll be on the hook for taxes on income/incorporation fees. I've read that if we have less than 50 shareholders, we can avoid a lot of legal trouble with Canada's Securities Act (but I am not a lawyer!). We'll definitely need a lawyer to take a look at the articles of incorporation. This stuff is expensive and takes time. I need to sleep on this, and think of a plan going forward.
At a glance though, this seems like a web of legalese.
I am a Canadian and my business is incorporated. Getting articles of incorporation is in the $1,500-$2,000 CAD range and is very straight forward as far as I know, it can even be done individually online (whether or not that's prudent is another thing). I do not know anything about < or > 50 shareholders, and the applicable laws however if the Corporation is controlled by non-resident shareholders, it is not considered a CCPC and there are different tax implications:
http://www.taxspecialistgroup.ca/public/taxtips.asp?n=11-02&site=tsg What I do not know is if "Transaction Verification Services" are considered an active form of income or investment income, the corporate tax rates here for each are considerably different.
The benefit to registering as a Canadian Corporation would be the corp would save the 5% GST charged for importing the miners here, and if I'm not mistaken the Corporation could claim back 5% of the hosting fee in GST; since no GST is charged in mining, it would be a full tax refund.
The issues are, as a non-CCPC there are no capital gains exemption (CCPC's are entitled to an $800,000 exemption on capital gains when selling their shares in the Corp.) And any income paid out by the corporation would be taxed AFTER corporate tax is paid (Canadians would get taxed as dividend income I believe, I'm not sure how Americans would be taxed).
For these reasons, a Group Buy where everyone is still an individual (with individual hardare using purchasing power together) would make more sense to me.