Coinbase is well known to randomly lock people out of accounts - they're the Paypal of Bitcoin wallets. They are likely associating accounts with 'bad' addresse

Coinbase is well known to randomly lock people out of accounts - they're the Paypal of Bitcoin wallets. They are likely associating accounts with 'bad' addresses and doing what you describe. The downside here is that a lot of people don't use Coinbase, i'm not sure what their upside is. They aren't exactly earning a reputation as a safe Bitcoin space.