Circumbinary Planet Formation

It's apparently really hard to form planetesimals where the Kepler circumbinary planets are. The planets we see likely migrated.
How not to build Tatooine: the difficulty of in situ formation of circumbinary planets Kepler 16b, Kepler 34b and Kepler 35b

Just that is why around circumbinary stars planetary systems are poor in planets and I do not expect much multis around them

Well these systems, in particular Kepler-34 and Kepler-35 have the gas giant located closer to the stars than the expected formation region for such planets (the ice-line would be further out), so some migration is pretty much expected. This work adds to the confirmation of planet migration.

I see no particular reason to expect the outer systems around these close binaries to be any poorer in multi-planet systems than single stars, unless of course these are binaries formed by Kozai migration + tidal friction in higher-order multiple systems.

Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion
http://arxiv.org/abs/1210.7757

Apparently the accretion-hostile conditions extend into the outer disc (4—10 AU). Circumbinary planet formation appears to be impossible without making some non-standard assumptions. Similar assumptions seem to also be required for the formation of S-type planets in close binaries.

Influence of the circumbinary disk gravity on planetesimal accumulation in the Kepler–16 system
http://arxiv.org/abs/1303.4598

(using the title from the PDF rather than the one with the mashed-up designation)

Including the gravity of the gas disc makes things worse.

Formation of circumbinary planets in a dead zone
http://arxiv.org/abs/1306.5241

Dead zones to the rescue?