Ironically, I wouldn't be surprised if this actually turned out to be less true in our heavily networked world than it was even ten years ago. These days, online networks and Internet dating sites make it far easier to meet people outside of one's immediate circle of friends then it ever was before. This fact could potentially minimize the utility of testing friendship groups, but it doesn't negate the other point of the article. People like to be in sync with their friends. If getting tested and talking about it publicly, or writing about where you used condoms, becomes the cool thing to do, maybe more people will get tested... and practice safe sex.