I think the Coinbase scam goes something like this.

1. You make your Coinbase Bitcoin purchase. The larger the purchase the better for them

2. Coinbase delays your coins by as much as 7 days and says the delay is because of BANKING ACH.  
    ACH does not take 7 days. If coinbase can get your money is 2 days, what is the point of waiting 5 more days ?

BECAUSE COINBASE NEEDS THE EXTRA TIME TO JUDGE THE MARKET BEFORE DECIDING TO SEND YOU BITCOINS OR NOT.
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3. If the price of bitcoin goes up AT ANY TIME FAVOURABLE TO COINBASE, Coinbase does not want to give you the coins,
   they prefer to keep the bitcoins and politely email you saying so sorry. It was high risk. Try again in a few weeks.
   We will keep the profit this time. Better luck next time.

4. If the price of bitcoin drops AT ANYTIME UNFAVOURABLE TO COINBASE, from the time you ordered, Coinbase would be happy
    to send you the bitcoins and for you to take the loss.

5. Coinbase can buy and sell bitcoin immediately and Coinbase clients cannot.
    We have to wait days sometimes a week. And usually never get coins.
  
6. Coinbase is using Coinbase clients money for their own profit by first blocking clients wins and keeping that profit  but also
    allowing clients losses. (also Coinbase profit)