It seems they are getting the royal treatment (ie: pounding with traffic) and they probably did not take into consideration that there network and or server might not be able to handle the traffic this offer would bring to them.
I am not sure if domainsite.com has a lot of customers but I feel sorry for the people who actually pay to register domains through them and cannot manage their domains due to this downtime.
http://www.whois.sc/domainsite.com <--- also currently shows their whois server to be down.
Thats why that saying comes to mind "There is no such thing as a free lunch".