I've thought on this a lot in the past and the only thing I have hope of addressing it is making any sort of personal/professional relationship spill overs societally verbotten. When folks are at work they intend to work and making any assumption against that line is just going to lead to pain. I really like the team I work with, but I don't ever want them to mix with the group I socialize with solely due to the fact that while at work I want to work.
You want to avoid even social (not just romantical) mixing?
Sorry, but I don't think this is viable with the workers I know (including myself). It is in head-on contradiction with the "do what you love" maxim that most people in my generation are trying to follow. We aren't robots and we don't want to live two completely disjoint lives (or, rather, when we do, we have internet forums, video games and what not for that). In order to have a job where I could completely dissociate from my coworkers, I'd need to find a second skill at which I'm good enough to find employment yet don't care enough about to let it bleed into my life. People are struggling enough with building one skill...
There is probably some good middle ground to be found (how far should my job be from my interests to avoid crossing the streams too much yet allow me to keep it? how much should I let my colleagues into my life?), but no one seems to have invested much in finding it.
There are some people who lean this way and that's fine - there's nothing wrong with it - but there are other people who don't. This will tend to follow an age distinction (with older folks being less interested in having more personal/professional crossover) but I strongly disagree with it being generational.
Your team at work will change over time and new people will join and leave, as you are forced to reconcile changes of employment with the destruction of your social circle I think you'll find that it's easier to move to keeping the two separate. Having children and a strong life partner can also contribute to this - there are a lot of relationships you care deeply about outside of the workplace and you don't want your time at work to be complicated by drama from the fact that you don't value your relationships with your coworker over that of your partner.
Social events at work can be fun and build a stronger team, but viewing your coworkers as your primary social circle probably isn't a healthy long term choice since at some point that relationship will be severed (hope that you don't have to fire a bestie) and someone will be left in an emotional lurch without a shoulder to cry on. I've found it quite helpful to be able to empathize with coworkers and chat about what's going on with work bits in a more safe environment but going into work hoping to find good relationships (social or romantic) is placing a large burden on those you're working with and can end pretty terribly.
I'd also point out that strong social bonds are a reciprocal thing and that while you may be entering the workplace hoping to form those bonds your coworkers may not and the visible existence of cliques in work that exclude some employees that may simply be uninterested in such social activity can lead just as easily to drama in the workplace.
