After some searching on the internet it seems the consensus is that the owner is Andrey Melnichenko (yes another Russian Billionaire)!  According to Forbes, he made his money in coal, banking, and chemicals in Russia.

An interesting find; it turns out he and his wife have a personal website – kind of an online biography of the two.  Kind of surprising considering the security risk this must create. However, nothing on the site suggest anything about the yacht – so the rumors could be wrong…