The Foundation failed to secure the hard-forked ETH against replay attacks, because it would be complicated. Instead they attempted to browbeat the exchanges into not allowing ETC trading.
Because the same transaction can exist on both the ETH and ETC blockchain, traders can exploit lazy exchanges and double spend ETC balances.
The replay attack vector was well documented, and all exchanges who hosted ETH wallets knew before hand how traders could screw them. Some (Poloniex, Bitfinex, and Kraken) chose to disregard the Foundation’s promise that ETC would never trade; these exchanges properly protected themselves from ETC replay attacks. Others (Coinbase, BTC-e, and Yobit) either naively trusted the Foundation, or improperly secured their customers’ ETC.
Any client who held ETH pre-fork on Coinbase, BTC-e, and Yobit rightfully demanded their ETC, or asked “Dude Where’s My ETC?”.
BTC-e said sorry not sorry. We screwed up. We trusted the foundation, and got essentially hacked of ETC. They told clients they could not honor their ETC balances.
Coinbase said they did lose ETC due to replay attacks on their GDAX exchange, but have 100% of all ETC due to clients in “cold storage” (whatever that means). Coinbase customers will receive their due ETC “in a few weeks”. Is Coinbase insolvent, doubtful. Coinbase is rolling in VC cash, so don’t worry your little head about them making good on their promises.
Yobit lost 40,000 ETC and didn’t provide any colour as to when or if these coins would be returned to customers.
Moral of the story, the Foundation has an agenda, and to trust them is lunacy. Those who did, got bent over Deliverance style.