/decloaks
Hubski is a de-facto cooperative. The content of Hubski is of, for and by its users such that the commentary and discussion of any external link is usually of greater value than the external link itself. Therefore, the content producers, the artisans, the attraction of Hubski is its community, not its leadership. Leadership, then, can be seen as the officers of a mutual benefit organization rather than as vendors serving customers.
Cooperatives do not function by donations, at least not in the traditional sense. Donations are best deployed in unidirectional situations where no reciprocation is expected or implied - earthquake relief, food drives, etc. For more bidirectional situations, such as church tithing, public broadcasting support, benefaction of the arts, etc, the organization generally reciprocates any donations with an in-kind gift to foster ownership and affinity - logo swag, limited edition merchandise and the like.
Hubski is substantially more interactive than the average NPR station and far more dependent on its users for its offerings than any church. That you're posing the question this way underlines your recognition of this. I believe a donation system will not benefit Hubski in the long run for the simple reason that donation allows one to "wash their hands" of their commitment to the problem when the continued maintenance and success of Hubski is the responsibility of all those who use it. Team Hubski has shown itself to be exquisitely sensitive to the desires of its userbase and offering a token "shut up and take my money" approach is likely to focus attention unduly on money. On the user side, things become "you have my money, do what I want." On the owner side, things become "we don't have enough money to do what they want, we need to panhandle."
If I were Hubski I would investigate cooperative charters. Shareholders are generally permitted votes and steering on a per-share basis, as well as the election of officers. These offices may or may not have the power to govern fundamental business decisions; often they function more as ombudsmen within the community. Fees for membership are determined via open calculation of operating expenses and necessary budget and any dividend at the end of the fiscal year is either divided amongst shareholders or paid forward into the next year's operating expenses. Shareholders often enjoy special privileges such as discounts on goods and services, preferential tech support, etc.
I would also investigate restructuring as a B-Corp or similar. Although largely symbolic, BCorps do provide a useful halo effect as well as encoding "don't be evil" into the DNA of the entity. There may also be tax advantages and municipal incentives depending on the site of incorporation.
/recloaks