Ever wonder why there were so few critters running around at the bottom of the ocean, even though there's plenty to eat down there?

Ok, you're not playing this game correctly. Now nod and say, "Why yes, Scott, I have wondered that several times."

Well, you may not have wondered about the question, but I'll wager you'll wonder at the answer:

Danovaro's team collected dozens of samples of sediment from sites around the world. Everywhere they looked the top centimetre of sediment contained large quantities of viruses. The average gram of sediment contained 1 billion viruses, which is the equivalent of 8 trillion viruses per square metre of ocean floor.

I wonder if perhaps the development of the nucleus, which distinguishes prokaryotes from eukaryotes, was driven by the need to escape from what presumably is this most ancient of arms races?