"Get the rich" is not a good justification for policy.
Do you have kids? It turns out one big economic incentive, particularly late in life, is to make money not for yourself but for your children. A lot of people hate the concept of an heir running around with money he/she didn't earn, but i mean, it's Not Your Problem so long as the money was fairly earned by the parents. Furthermore, a billion dollar estate is probably something that has already been taxed, possibly several times, possibly in a compound fashion, so I don't think there should be any worries that rich heirs have not paid society for their money.
There's also serious implementation problems with estate taxes, as other posters have described. Levying very large taxes on illiquid and hard-to-value possessions is unfair no matter how you slice it.
I don't want to defend the handling of this particular estate, but the justification for estate taxes in general is that it is counter to the interests of a democracy to have a hereditary aristocracy. It's not just that we hate the idea of trust fund babies -- they actually hurt America.
> A lot of people hate the concept of an heir running around with money he/she didn't earn
I don't hate the concept either, but IMHO complaining that one would only receive $500M of unearned money instead of the $1B anticipated just makes the would-be recipient look like an asshole.
Most people in the world would probably be satisfied to receive a few thousand dollars of unearned money. $1M and they'd be set for life in most parts of the world. Anything above that is just gravy.
Do you have kids? It turns out one big economic incentive, particularly late in life, is to make money not for yourself but for your children. A lot of people hate the concept of an heir running around with money he/she didn't earn, but i mean, it's Not Your Problem so long as the money was fairly earned by the parents. Furthermore, a billion dollar estate is probably something that has already been taxed, possibly several times, possibly in a compound fashion, so I don't think there should be any worries that rich heirs have not paid society for their money.
There's also serious implementation problems with estate taxes, as other posters have described. Levying very large taxes on illiquid and hard-to-value possessions is unfair no matter how you slice it.