Value-for-value is really donation-for-donation
It’s a gifting society
People put in the work, whether that be an article, video, or client
The input is time, energy, capital
In exchange people zap them, whatever feels right to them at the time in terms of amount, direct to their wallet
The output is stored time, energy, capital
This then begs the question: if one’s entire annual income is a donation, do you owe tax?
Then… when ‘donating’ with a zap, is that tax deductible, to counter the tax payable on zaps received? 
Great question. So as the donor, could you write that off as a cost?
I think the recipient of your "donation" has to be able to offer you a gift aid type option to give you something the taxman views as a write off.
😅 Good question! Depends on the tax law. In Europe you often have certain limits for donations that are tax free. But if you aggregate many small to a bigger sum then the tax office could become greedy again.
I'm not a tax expert but from experience in Spain you have to be an association IE a form of charity to specifically handle donations.
Otherwise, whatever you receive, it's all income. Even 21% tax due on receipt of crowdfunding. They say it's "available capital", robbers.
