antihenry
CAF GRU Rep
He (and his supporters, not always with his involvement) has a history of making stupid and illogical political decisions. In the current situation, when the levels of hatred are over the top (don't tell me you don't feel it yourself), it's more than possible that some of his followers decided that he isn't a patriot and doesn't deserve to live. I don't believe that Putin himself was involved - as you and others said, he was very much yesterday person and didn't possess any threat to regime. @Raoul overestimates him because Nemtsov (much like Kasyanov and Kasparov) is very west-oriented and was more concerned about his image as an opposition leader on the west than actually in Russia.
Putin gains absolutely nothing from killing Nemtsov but his death gives a whole lot of ammunition to his detractors, especially outside of Russia. Like I said, I'm no fan of Putin, but he isn't stupid and if he really wanted to do something about Nemtsov, it would have been much easier just to arrest him on some charges and send him away, like he did with Khodorkovsky, who actually had the kind of money, influence and political ambition that Nemtsov couldn't have dreamt of, even in his heyday.