1. teens because they're not allowed out of the house to hang out with their friends and if they are, their friends aren't or they have to go to highly regulated and supervised settings
2. college students because they know that they're supposed to be in class/doing homework/sleeping, but they're procrastinating because talking to friends is much more fun and a little bit of low-level talking through FB can be justified far better than meeting up with someone for a coffee
3. white collar workers because they're bored at work and want to hang out with their friends when they should be doing a variety of other things
4. nightshift/hourly service workers because their friends work different hours
5. parents at home because they can't really go and hang out with their friends because babysitting costs too bloody much
6. highly mobile adults and military folks because their friends are far away, probably in a different timezone and getting together in person can only take place sporadically

What we've found in our research is that there are two organizing principles of online socializing practices: interest-driven and friend-driven. People who are interest-driven (lovingly called "geeks") seek out people who share their passions, regardless of location, and thrive on access to the technologies that connect them more broadly to others of their stripe. As much as we'd love for this to be everyone, it's not... Most people are not primarily interest-driven in their social practices, although many have a portion of their social practices that fit into this category. The majority of people and the majority of practices are friend-driven. This means that interests are derived through friends, not the other way around. This is why most people go online to connect to people that they already know to reinforce relationships that they already have. At best, this cohort will leverage the technology to meet a friend of a friend (just like at a good dinner party).

The largest exception is quite obvious: sex. By and large, when people leverage the technology for sex, they don't want to engage with people that they already know. The second notable exception is more intriguing: health issues. Interestingly, even the most friend-driven people seem to switch to interest-driven practices when it comes to needing support for an illness or help in gaining information around said illness. It should be noted that these are not common amongst teens and interest-driven practices are almost exclusively the domain of geeks and other socially marginalized and ostracized teens.