Coinbase blocked my personal account, holding my Bitcoin until I provided photo ID. Just to get access to my money already purchased.

Then they incorrectly decided my immigration status and removed my bank connection.

I closed my account and asked for my inappropriately obtained information to be deleted. They refused to "protect" me from "identity theft". Screw them.

r/bitcoin also has a vendetta against Coinbase because they're for a blocksize increase. That forum is actually incredibly childish (just read the comments). You don't find the same concentration of complaints in other cryptocurrency reddits, and r/bitcoin definitely is not the only one or the most important.

Coinbase CEO here. This is (sadly) quite accurate.

The other reason you see so many complaints there is that there are many scammers trying to buy digital currency with stolen credentials, and a common scammer tactic is to appear angry (via support channels, or any public forum) in the hopes that we will approve their purchase.

Nah you're just too busy pumping ethereum

Which is the most important?

"Multiple withdrawal when only one was instructed" - I believe this was because they were using MongoDB in the early days for financial transactions.

Happened to me 2 weeks ago. I got a call from my bank asking for approval to send back the duplicate transfer after one week. For a second I hoped they will not notice :) After this I don't trust them to handle my money anymore.

Quoting from circle.com:

  No fees to move money, and no limits on how much you send or
  receive each week using your Circle account.

Naive question: how do they make money?

Bid/ask spread on the price of selling/buying bitcoin for dollars.

And what's the spread like? Fixed or otherwise?

Very easy to use Circle to purchase bitcoin with a regular card, then move that bitcoin to your own external wallet. I can recommend this as a smooth experience.