You'd think with a big exchange like that would be fully prepared for DDOS attacks, but instead this is the second time within the last months or so. Personally, I wouldn't trust to leave my money there and you wouldn't even know where it's gone!!
Even google and facebook had their downtime, 100% uptime is a myth and a sign you did not understood the the technology itself.
There is no way to proof a system or program is bug free - that it *is* impossible to determinate is the first and fundamental law
of the whole computer science and every information related science too.
That is btw the point you should consider to move your home when someone tells you that the computer system controlling the nuclear power plant next to
you is "100% safe and tested".