Yesterday new users of one of the most popular cryptocurrency exchange Bitfinex had faced unexpected issue with registration. Now in order to create an account, new users need the "invitation code".
Bitfinex Sign Up Form
As you can see on the screenshot above, there isn't a lot of information what is "invitation code" and where should new user get one. On the Reddit thread even users with old and active accounts aren't able to find a code to share with a friend.
There are no invitation codes. Bitfinex is probably trying to halt all new registrations without publicly saying as much. Given the other dodgy things of late (warrant canaries, withdrawal minimums), it might just be that they're about to get shuttered. FBI? FINCEN?
xpanda70 from Reddit
It is worth noting that there is no information on the new registration rules in the official Twitter account.
Registration and account validation on any of the cryptocurrency exchange is not an easy deal at all. For example, at Poloniex, you need to provide the scan of your ID and and a clear photo with you, your ID and "Poloniex" on the piece of paper. And photo must be 100% clearly visible.
Poloniex Account Verification
Another popular exchange called Bittrex decided not to bother itself with "invitation codes" or collecting photos of new users. They just stopped new users' registration five days ago and still hadn't open it again.