The crypto exchange CEX.IO is following suit and doing what Bitfinex is attempting to do: temporarily staying away from taking new users in as their exchange engine and support staff is overloaded.
They cite their long term strategy of providing the best possible service to their customers as the reason - they are not keeping up with the explosive growth in crypto space.
As 2017 has shown explosive growth of interest to cryptocurrencies […] Our user base grew 200% this year.
The inflow of registrations, however, has put additional pressures on our support and verification teams. To maintain security […] we choose to stick to our strict AML and KYC policies, even if it comes at the expense of on-boarding speed.
Our KYC and AML procedures impose a certain amount of time required for each registration to process […] we choose to temporary pause new registrations and allocate extra efforts and resources to processing the current queue.