As Nova-Exchange doesn't trade in Fiat-currencies, there is no need to have an official registered address, or a formal company - everyone could start a purely online trading company with a internet connection and adequate software... And suing many other exchanges - even with official addresses - might prove difficult... So never leave large amounts of crypto at an exchange (except if you are running your own... 
).
).Of course there is no need for registering a company, but the questions remain the same:
1. Why they are lying about being a registered Swedish company operating under Swedish law?
2. Why they are hiding their identity?
3. Why they are blocking users without notifying them via email? (the news section is blocked too)
4. Why they haven't given any information or status updates about the IP blocks or hacking attempts on twitter or facebook yet?
5. Why their support isn't reachable without being logged in?
6. Why there's no update about the situation since the 8th of September (six days!)?
7. How could you know, their claims about being hacked are genuine? They lied once...
8. Do you think their behaviour is just highly incompetent or do they know what they are doing and all this is intentional?
Trust your gut feeling! Would you do business with this kind of company in real life?
In my opinion, this novaexchange thing will go ugly any time soon!
Update:
https://www.reddit.com/r/Domain/comments/6yv9u8/did_novaexchangecom_just_steal_my_bitcoin/dmwbkyz/
"I'm able to log in now but I a unable to remove any coins because I never, ever receive the confirmation email. I've been trying this every day for the last few days."