how do you plan to cash out your investment from the immortal Em society when they decide not to honor your 10^26% compound interest?
Why would you assume investments won't be honored?
As Hanson points out, we could rob our retirees of their investments. This doesn't actually happen because "non-retiree" is a shallow category that doesn't make for an actual functioning political/military coalition. Note that right-handed people are a large majority and could form a political coalition to rob left-handed people of their money. Yet this hasn't actually happened.
He was talking about Ems at the equivalent of .3mm space living 500 years in a month. If you invest when we start seeing a 1 month doubling period and cash out two weeks later, then that's longer than America's been a country. Two months later goes back to before the dark ages, four months is the death of Jesus, and holding on to your investment for a year is basically the entirety of recorded civilization. If you had a time machine and went back and invested in any of those time periods, what are the chances you'd get that money back?
Hanson's analogy ...
Lecture at youtube.
Sorry - haven't watched it yet so no summary, but I expect it to be fun.