Berkshares appear to be a glorified version of Amazon vouchers, exchangeable at participating stores for a fixed dollar value. Except you can probably buy more with Amazon vouchers, and they probably look more like dollars.
On the other hand, the creator of Liberty Dollars campaigned for the abolition of the Fed whilst minting coins which were arguably similar to rarely-circulated commemorative dollar coins also called Liberty Dollars, and stamped a dollar value on them (which of course was in excess of the bullion value he was supposedly backing them with). Then when the US Mint issued warnings about "illegal coins" he took the suicidal decision to sue it to try to force it to withdraw them. Not a surprise that the government eventually found grounds to prosecute him under relatively obscure constitution-linked statutes covering exclusivity of coin mintage. (They also confiscated a lot of coins, most of which were eventually returned by courts. They're worth more now than when they were minted due to rarity value, looking pretty, and coin collectors and libertarians wanting them to show off)
There's a cautionary tale for the crypto-world there, probably.