Facebook treats friends as a single homogeneous group even though people on Facebook are possibly acquainted with diverse group of individuals and perceive their friends as representatives of different groups. It is a common observation that people tend to select friends with similar characteristics or individuals are likely to change their attributes to conform to their friends. In this measurement study we quantify the extension of this behavior on Facebook. We measure the probability with which a friend belonging to a particular group of friends will or will not comment on a post that has already received comments from other friends belonging / not belonging to his own circle of friends. To this end we collected an original data set of Facebook profiles of 50 volunteers. Our data analysis shows that Facebook users are influenced in their choice of posting comments on friends' wall posts, based on whether or not they are acquainted with the people that left earlier comments. Identification of such behavioral nuances can be helpful in improving the user interface design of online social networks.