Agreed. Maybe one day they will be so big that they are deemed "too big to fail" like the over-extended failed big banks and the bailouts/TARP of the Great Recession.
If the government seized funds of Coinbase with how entrenched it is even now, there would be massive legal challenges. Ultimately that might be a good thing in terms of forfeiture reform. Coinbase (US company) is orders of magnitude different than btc-e or mtgox etc.
Nothing like that would happen today though as that was more a reaction to the Great Depression and the wealthy hoarding during times where cash was constrained.
Also, that was gold so who is to say that couldn't happen to gold today if it can happen to cryptocurrencies, any hoarding would be a target in another depression that bad much like things like offshoring might be or are in some case.
Why it won't happen today you can base off the reaction during the Great Recession, we bailed out failing banks with TARP that got us into this mess by over-extending leverage instead of consumers. The FDR order helped the economy and all people at the time over the wealthy.
FDR, if he was in charge during the Great Recession, probably would have made new banks and let them fail if that happened under him, a people's president. The SEC was also created during his admin which is arguably the best thing to ever happen to investing in the US, solid markets since Securities Act of 1933 and SEC inception, cryptocurrency will eventually be more closely regulated as it grows.
