According to the Russian internet publication Obozprevatel ("the Critic"), shown in the photographs are colleagues of the provocative Russian-Ukrainian performance artist Oleg Kulik who "conducted their own Moscow own protest action recently, commemorating not only the larger and more well-publicized 'March of the Dissidents' but also the 46th birthday of Mr. Kulik, as Oleg himself reports on Invivio.net."
Apparently the group was inspired to enact their own unique sort of protest action by mounting a mattress on the roof of a car and then driving it through the streets of Moscow while copulating after witnessing the Moscow protest action last weekend led by dissident politicians Garry Kasparov and Mikhail Kasynanov as the "Other Russia" coalition. It seems they wanted to emphasize the "make-love-not-war" theme in the most visceral manner possible.
According to the participants, they received a much more "sympathetic" response from the local police than was the case in regard to Kasparov's forces; the cops they passed only laughed and waived. Wisely, it seems, the participants somehow managed to refrain from referring to Vladmir Putin at all, not even as the nation's "phallic symbol."
One can also see this as a significant commentary on the Other Russia protest itself; the ragtag protest groups that comprise it are badly organized, poorly funded, and receive scant Western media attention except when there is violence or when somebody prominent like Kasparov gets arrested. Their platforms are not widely available in English. The turnout for the followup protest in St. Petersburg after the major crackdown in Moscow was atrocious, easily crushed by the Kremlin's heavy-handed tactcs, and the action largely ineffective. State-owned Russian TV broadcast virtually nothing about the events, and one must wonder what the protesters would in fact have to do in order to register such coverage.