Social networking sites experience huge growth in their number of members. For marketing purposes they are very beneficial to spread Word-of-Mouth in terms of product recommendations. A closer view detects that social networking sites can be divided in open- (OSNs) and invitation-only social networking sites (ISNs). Their members may behave different in contributing knowledge in terms of product recommendation depending in which social networking site they are currently remaining. We therefore first analyze if the members are willing to recommend products for either monetary or non-monetary rewards in their preferred social networking site as well as if they consider these recommendations in their purchasing decision and connect this to a member’s personal- and community-related outcome expectations. Second we compare the results between ISN- and OSN-members to conclude in which type of social networking site a product recommendation should be monetary rewarded or not.