What is seen as fair is a very subjective question. I would prefer not calling it "fair share" because taxation is very complex and depends hugely on how good you are at gaming the system.
What's the capital gains tax in the US? I seem to distinctly remember it's far lower than a bricklayer's income tax. So, arguably, taxes on bitcoin speculation are not a "fair share" only in the sense that it's still too low.
If you want to go make a million dollars, more power to you, but you also need to pay your fair share like everyone else.