  We study the issues of existence and inefficiency of pure Nash equilibria in
linear congestion games with altruistic social context, in the spirit of the
model recently proposed by de Keijzer {\em et al.} \cite{DSAB13}. In such a
framework, given a real matrix $\Gamma=(\gamma_{ij})$ specifying a particular
social context, each player $i$ aims at optimizing a linear combination of the
payoffs of all the players in the game, where, for each player $j$, the
multiplicative coefficient is given by the value $\gamma_{ij}$. We give a broad
characterization of the social contexts for which pure Nash equilibria are
always guaranteed to exist and provide tight or almost tight bounds on their
prices of anarchy and stability. In some of the considered cases, our
achievements either improve or extend results previously known in the
literature.
