For the moment, BitMixList and the onion site are both down. The server is not responding, but I cannot confirm whether it is a DDoS. I'm working on fixing this issue.
Sorry to hear this but I know some guys who own regular website unrelated with bitcoin and it get's ddos attacks all the time.
Shutting down websites can be profitable, but some people are doing it for fun, believe it or not.
Why would anyone be so interested in that, especially when there are so many other lists on the internet doing fine?
I don't know the real reason, but you can only imagine how they are attacking bitcointalk forum and other services all the time.