While the Federal Reserve has been playing "buyer of last resort" in snapping up agency mortgage-backed securities throughout the crisis and beyond — through three successive rounds of so-called quantitative easing — the government hasn't been the only buyer.

Perhaps no other investor has gone all-in on agency MBS to a greater degree than has Pacific Investment Management Co, or Pimco.

Call it "shaking hands with the government," because that's what Pimco co-founder Bill Gross has called it. Reuters has an in-depth look at the strategy, and the massive payoff it netted for the asset manager and its investors.

There is no evidence of illegality or impropriety in Pimco's actions. Pimco says that it kept its employees who were helping the Fed at arm's length from those investing for its funds, and that its bond-buying bet was conceived before the Fed's program was begun. The Fed says it implemented and enforced strict controls over the trading done by the firms.

But Pimco's ability to enrich its returns by following the Fed does illustrate how the Fed's easy-money policy over the past five years has produced outsized winners. As one of them, Pimco benefited enormously from the very Fed policies that it was helping to implement.