1) Providing the username and password for online access to the bank account; or
2) Allowing Coinbase to make two micro-deposits to the bank account, and then providing the correct amounts of the deposits when they are received.
Maybe it's possible that so many people are signing up for Coinbase right now that it's flooding out the fraud?
They would. However, typical ACH fraud entails pulling money using only the routing and account numbers, which can be found on all paper checks; this mechanism prevents that.
It's really quite shocking how a ecosystem that touts decentralization has a glaringly centralized failure point - the fiat exit exchanges. When one or two of them goes, it will bring down the whole house of cards. And given how shitty CB's software was (or maybe still is) I just hope I can get my gains out before the whole thing comes crumbling down.
The Discorientating Use of the Word "They": https://www.youtube.com/watch?v=i_xVAqJ-NY0
I am an insider in the Bitcoin industry, and within 1 day of opening a new bank account we started seeing fraudulent wires flooding in. When we dug deeper, it was shocking to see how many Americans' bank credentials have been hacked. It takes almost no effort for a EEU/RUS hacker to send a wire from a hacked bank account.
Once the fraudulent wire is sent, rest of the wire transfer system is tediously manual. So wire network participants simply choose to block bank accounts that receive repeated bad wires. This is why Wells Fargo cut out Bitfinex and Visa has decided to stop working with Bitcoin companies.
ACH fraud is even more rampant because you can pull money from someone's account without their consent (as long as they don't notice/contest within certain number of days). Coinbase profit margin is 0.5% per trade, so they need to keep their ACH fraud rate below that number to not lose money. ACH fraud rate is well over 1% industry-wide. This is why I strongly believe that Coinbase has to be losing massive amounts to ACH chargebacks.