Nick Beckstead’s thesis “On the Overwhelming Importance of the Far Future” deals thoroughly with these questions from the perspective of Effective Altruism (albeit within the framework of a Philosophy PhD). See especially chapter 4.
http://tinyurl.com/BecksteadFuture
Working through the thought experiments he presents and seeing the different unintuitive consequences of each theory changed my mind: I had strong intuitions that creating extra happy lives had no moral value, but I’m now convinced that doesn’t make sense. I also agree with Ryan that the question becomes less about what is worth adding and what isn’t, and more about what we fundamentally value and whether that will be increased.
Turns out tax deductibility is much more complicated in Australia than elsewhere, and is made even worse by the fact that a couple of legal challenges are currently underway, so the case law is in flux.
There are a couple of people in Melbourne (not me!) who know their way around the tax system very well and are planning to write up the parts that would be relevant to setting up a re-routing fund. I think they’re not prioritising it because setting up such a fund looks like it would be at least 1 full time job, plus a decent amount of accounting/legal/senior-community-figure support.