This study examined the role of Facebook friends lists in identifying potential sexual and committed relationship alternatives and the effects this had on relationship investment in a sample of 371 young adult undergraduates. A Facebook versus memory experimental protocol was developed to test whether Facebook friends lists act as primers for recognition of potential sexual and committed relationship partners and whether identifying these potential partners (either from Facebook or from memory) caused lower relationship investment. Facebook friends lists did act as memory primers for potential partners, but only for sexual partners, and the effect was stronger for men than it was for women. However, identifying potential partners through Facebook actually lowered a person's perceptions of the quality of their alternatives. In contrast, merely thinking about potential alternatives from one's social sphere lowered relationship satisfaction and commitment with one's current committed partner. The implications of these findings are discussed in relation to current work on the negative effects of Facebook use on relationship outcomes.