I believe, from my reading of the discussion, that the others are attempting to point out that the existence of a tax does not premeditate the enforcement of a tax.
Bottom-up funding has its place: such corporations survive by benevolence (taxation agreed upon by members with transparent benefits) or malice (exploitation of newcomers/less observant pilots who leave quickly, but might bring additional tax-cows in before they go). Their success depends on a variety of factors, but benevolence is the long-term winner due to sustainability and transparency inviting comment form the more numerically gifted line members (who may rise through the ranks as a result).
Similarly, top down (my corp model) is very effective. Paying members for work done is a matter of negotiation and transparency, but the ISK flow is reversed. Similarly it can be benevolent or the ISK is essentially a paltry appeal to the 'employability' desires of vulnerable pilots (malicious).
These are independent of the factor you, Ria, bring into the equation - the concept of service. Service through time spent is arguably the most precious resource in EVE and highly active contributing corp members (especially those with few roles nor desire for them) are fought over quite literally. However, as I have pointed out the concept of service is independent of ISK income. It may contribute ISK or drain ISK, depending on the activity. If self funded (by the beneficent pilot) it may have no net effect.
Realistically a corporation will be the sum of choices made regarding the expenditure of time and isk, and the accumulation of players, talent and (you guessed it) ISK. ISK, used in this discussion, refers to any income stream - so minerals/materials/moons/LP (anything that can be taxed by mechanic or by domination of the source). The decision to tax or not to tax is freely made, from 0-100% and some corporations (houses of cards) fall by their ill-intentioned over taxation of line members. Others prosper by feeding back in a manner that exceeds the perceived loss of income that taxation represents.
Players may game the system as you, Ria, have mentioned. They may have tax-evasion corps, and some CEOs (like myself) won;t mind this. Others that do will soon learn a harsh lesson in the woeful inadequacy of API checks to enforce some fiscal regime. And so even after a tax is applied to a resource - it is purely optional. You can participate in it in good faith (if you feel it is worthy), leave, or evade at your leisure.
So my question to you, directly, would be:
"Considering that you can choose not to tax a thing (LP for example), what is the downside of there being an option to tax it?"
My thought is that the addition of a multitude of taxes (hello Citadels) will provide options. Poorly executed they will annoy, wardecs may fly or stations lie fallow (and corps burn) as people say no to the tax. Well planned and communicated, they could form the foundation of community investment (market seeding/free-ship fleets funded by loyal custom or membership). Yes these things can already be achieved through other means, but honestly, what is the downside of choice?
To me that is the crux of the matter. Choice. Having it, even if that choice can be a bad one to make in some scenarios, opens up the sandbox a little more. It allows more emergent game play as movements around the issue rise and fall. And if all it takes is an additional variable and function in a class within the game code, I think that's a small cost for a world of choices.
