Imagine the life of your average person from, say, 500 years ago. The got up at the crack of dawn, did the morning chores, went off into the field and worked for the whole day before eventually coming back to the house for a late supper. This was well before home electricity was common, so there wasn’t much a person could do after the sun set. They spent much of their waking hours doing whatever their job was and often would define themselves in those terms. “I am a farmer.”
Now let’s jump to 100 years ago. Still a lot of work, but not quite to the sunup-to-sundown levels from before. There’s a little more room for entertainment, and a broader selection of jobs available. But they weren’t fully consumed and/or defined by their work. Maybe they sang barbershop on weekends, or took the family out for a ride in their new automobile. Whatever the case, the point is that they more ways to identify themselves, and might even adopt different identities depending on the context.
There is a diffusion and shift of affiliation, belonging and identity in the emergent business context, relative to what has come before. The transition to a context where people in general have more connections, but a smaller proportion of weak ties, means that affiliation is diffused. While a person might cowork with a larger constellation of people, fewer of those coworkers are likely to be connected to each other. This is the nature of loosening the network, even while increasing the degree of connectedness for each individual.
That's a little dense, but what he's basically saying is that we're more connected now than we used to be. We have more contacts with more people in a wider variety of ways. The people I know working for MTV, for example, don't perfectly overlap with the people I know from writing about comics, despite being very similar types of groups. Extending that idea, those are both different groups from co-workers from other jobs, my family, my signifcant other's family, my friends from school, people I know from the gym, etc. I have a wider circle of people that I come into regular contact with.
The other part of what Boyd is saying, though, that those contacts generally aren't as deep. Whereas we used to live down the street from our co-workers and hung out with them after hours at a local bar, we might now live hundreds of miles apart and never see each other socially. What happens as a result of that is that we're not as integrated into each others' lives and only deal with each other in the context of a specific identity. I deal with this person strictly as a colleague and that person as a gym partner and this other person as a relative. The relationships aren't as deep and, therefore, tend to be more role-specific.
NPR started a series in Aprial called Code Switch that speaks to that idea. Originally, the notion of code switching was linguistic in nature; how someone might switch from one language to another. They're using the phrase more broadly: "We're looking at code-switching a little more broadly. Many of us subtly, reflexively change the way we express ourselves all the time. We're hop-scotching between different cultural and linguistic spaces and different parts of our own identities — sometimes within a single interaction."
All this relates to fandom in how any given fan might act in a different situation. You've seen that "What people think I do..." meme? That speaks to this notion of code switching. As a fan, you act (and are perceived) differently around different groups. Relatives might not see the positive emotional benefits of your hobby and view it as a waste of money, and those you only meet at conventions only see your final works without a real appreciation for the amount of time and resources you may have put into things. As an individual, you're going to inherently react differently to those people in those situations and, before long, you're going to come to expect those types of people when you encoutner similar situations later. You begin to mentally code switch to another role.
These different identities can make things challenging for a fan. Back in the early part of the 20th century, finding another person who liked comic books the way you liked them was so hard that anyone who read them was a welcome addition. With the increasing number of identities we're able to (and often) adopt, and in no small part thanks to worldwide communications we have at our fingertips, we're able to distinguish between fans who like Firefly because of the sci-fi/Western asthetic and fans who like Firefly because it showcases a group of outsiders who elected to become an ersatz family and fans who like Firefly because of Joss Whedon's sharp dialogue and fans who like Firefly because Nathan Fillion is attractive.
There's nothing wrong with switching between identities, of course; it's quite normal and everyone does it to some degree, emphasizing certain character traits more than others in various situations. The key, it seems to me, though, is to be self-reflective enough to recognize how, when and where you code switch while you're in fandom, and thus be able to mentally and emotionally align yourself better to whatever group you happen to be with.