  In many coalition formation games the utility of the agents depends on a
social network. In such scenarios there might be a manipulative agent that
would like to manipulate his connections in the social network in order to
increase his utility. We study a model of coalition formation in which a
central organizer, who needs to form $k$ coalitions, obtains information about
the social network from the agents. The central organizer has her own
objective: she might want to maximize the utilitarian social welfare, maximize
the egalitarian social welfare, or simply guarantee that every agent will have
at least one connection within her coalition. In this paper we study the
susceptibility to manipulation of these objectives, given the abilities and
information that the manipulator has. Specifically, we show that if the
manipulator has very limited information, namely he is only familiar with his
immediate neighbours in the network, then a manipulation is almost always
impossible. Moreover, if the manipulator is only able to add connections to the
social network, then a manipulation is still impossible for some objectives,
even if the manipulator has full information on the structure of the network.
On the other hand, if the manipulator is able to hide some of his connections,
then all objectives are susceptible to manipulation, even if the manipulator
has limited information, i.e., when he is familiar with his immediate
neighbours and with their neighbours.
