I think it's cool when groups of friends pledge the same sorority, since they've already bonded and their enthusiasm can spread to the rest of the chapter. However, it can go both ways...there were several girls from one sorority on my campus who had been friends since high school, and one of them got in trouble with standards over something she didn't feel she should have been called in for. Her friends supported her, of course, and
all of them ended up deactivating.