Ask HN: Who are Russian Investors?

While reading article about Plastic Logic's 700m investment, I noticed another major investment by 'Russian investors'. There seems to be a gigantic amount of investments by Russian investors in last few years (not only in tech like facebook, zynga but also in real estate etc.. google for more).

You don't hear so much about investment from investors from other countries (say Chinese/German/French investors). Does anybody know whose money is referred to as when we hear the term Russian investors? and more specifically, how they have this much free cash to invest (given Russia isn't obscenely rich)?