I transferred a domain to CoinDomains not long ago. I am/was happy with the service - the transfer completed and my domain is working. Their website is down on my side, too.
Before transferring the domain, I expressed my concern in an email I sent to admin at coindomains.net: "If for some reason Coin Domains goes out of business in the next year, what would happen to my domain?". In a reply, it was explained to me that...
In regards to Coin Domains closing, the likelihood of it happening is very low. Even so, it's good to have backup plans. As such we have a system were if our admin panel does not get logged into for 2 weeks, an automated message is sent out to all clients with details on how to recover domains.
I'm not sure how well that system works if their server is fully down - and of course it may be complete marketing/scamming BS. According to the status and authorization request emails I received while the transfer was being processed, I understood Coin Domains was a reseller of Internet.bs, at least for the .com domains:
Internet.bs Corp. has received a request from Coin Domains on September 5, 2012 for us to become the new registrar of record.
(Internet.bs is a fairly well-known and established registrar with great prices. I'd have gone with them if I wasn't paying in bitcoins.)
Assuming that two-weeks-timeout recovery system is not a lie, that the "admin panel" and timeout-recovery-system is the one on Internet.bs side, and that nobody logins into that panel for the next two weeks, then I think we should all receive an email from Internet.bs asking us what to do with the domains, in two weeks.
I'm assuming that Coin Domains simply used Internet.bs' reseller API:
https://internetbs.net/ResellerRegistrarDomainNameAPI/It mentions no recovery system, but (and since at least my domain has already been paid, or it would have gone down already) the domains are paid so I wonder what Internet.bs can do if a reseller goes out of business. IMHO, ideally they should be able to transfer the domain to an internet.bs account of your own, free of charge, so you could manage your domain.