We study sequential voting with two alternatives, in a setting with utility externalities: as usual, each voter has a private preference over the candidates and likes her favorite candidate to win, but additionally, a voter values voting for the chosen winner (which is determined by the majority or super-majority of votes). This model aims to capture voting behavior ("likes") in social networks which are publicly observed and sequential, and in which people care about their "public image" as determined by their votes and the socially accepted outcome (the chosen winner). Unlike in voting with no externalities, voters act strategically although there are only two alternatives, as they rather vote against their preferred candidate if the other is to win. We present two rather surprising results that are derived from the strategic behavior of the voters. First, we show that in sequential voting in which a winner is declared when the gap in votes is at least some large value $M$, increasing $M$ does not result in the aggregation of preferences of more voters in the decision, as voters start a herd on one candidate once a small lead in votes for that candidate develops. Furthermore, the threshold lead for such a herd to start is independent of M. Secondly, we show that there are cases in which sequential voting is strictly better than simultaneous voting, in the sense that it chooses the most preferred alternative with higher probability.

Multi-level marketing is a marketing approach that motivates its participants to promote a certain product among their friends. The popularity of this approach increases due to the accessibility of modern social networks, however, it existed in one form or the other long before the Internet age began (the infamous Pyramid scheme that dates back at least a century is in fact a special case of multi-level marketing). This paper lays foundations for the study of reward mechanisms in multi-level marketing within social networks. We provide a set of desired properties for such mechanisms and show that they are uniquely satisfied by geometric reward mechanisms. The resilience of mechanisms to false-name manipulations is also considered; while geometric reward mechanisms fail against such manipulations, we exhibit other mechanisms which are false-name-proof.