[dragonwriter]

> Bitcoins are far more practical than an S&P500 ETF. For instance, I can carry bitcoins across a border, whereas if you want to move shares across a border it will involve a lot of paperwork -- if you are a US citizen it may be impossible due to FATCA.

You seem to be comparing like what is physically possible with one with what is legally allowed with another; it's physically possible, and you'll probably usually get away with it, to carry stock certificates across most borders. Conversely, I haven't seen ant set of customs allowances which permit travellers to legally carry bitcoins across the border (and those rules tend to be “everything not specifically permitted is prohibited”.)