It's perfectly reasonable to assume $600 million has flown in via Taiwan. Note that that doesn't mean that local Taiwanese have personally bought $600 million. Tether creates an arbitrage opportunity. If you have a Taiwanese bank account, whenever Tether gets out of sync, to say, 0.99, you can simply arbitrage that away and make a risk-free profit. That is what is happening. The demand isn't coming from Taiwan per se, it's coming from arbitrageurs (who either are Taiwanese, or are using someone who has a Taiwanese bank account).
You sound like you are living in the US, and everything is simple there and works as described. Which is probably true for you, as I understand those are exchanges catered towards US customers. However the mistake is that you assume that the rest of the world (majority) works the same way.
Bugs. I have discovered two bugs personally, reported them to Coinbase, and those are still unresolved.
For context, I reported couple of bugs to MtGox back in the day, and even MtGox fixed them in under a month which is more than what I can say for Coinbase. I guess this is what happens when Coinbase speed-hired 100 people in one year with no proper team-building exercises.
Mostly that if anything goes wrong their support tends to be incredibly unresponsive. Also make sure you're not using SMS-based 2-factor authentication with them since there's a long history of people getting their phone numbers stolen and then their Coinbase accounts drained within minutes.
I had the same experience. Got locked out of 2FA, spent two weeks waiting for a reply from support, only to be told that I should just make a new account. Unfortunately I haven't found an easier option for buying BTC.
I had the opposite experience, though this was before Coinbase created/supported recovery codes for 2fa. My phone with the 2fa app bricked and it was a painless, one-message exchange with Support to work around it, completed in < 1 business day.
I can confirm: my 2FA has been hacked on Coinbase. My Social Security number + DOB are out on the internet, and it makes it trivially easy to hack companies with poor security protocols like Coinbase, Authy, AT&T, TMobile, Comcast, Yahoo.
On the account draining -- well, there's a latency in setting up new bank accounts there. So I'm surprised it's that easy to just yank money out.
Although I did notice there's no account verification. For example, on Vanguard or other platforms they do a small deposit of a few cents and ask you to verify the payment amounts, a process which has a latency of a day or two.
