Conferences are like giant weddings. Everyone you met there is somewhere in the spectrum of guests, people from your life you typically bump into.
The PhD adviser is more of the parent you are meeting after a long time. You go have dinner, talk about work and life. He tells you how to win people at the new job (in-laws), because what I do reflects on his training. Beaming with pride, he goes around introducing me to everyone. The pride on his face, and my occasional embarrassment felt similar to when a smart kid from town cracks the IIT-JEE exams, and their parents go about beaming in pride and showcasing their kid to every (highly disinterested) neighbor, distant relative, and visitor. I am more like the academic child.
Grad school friends/classmates: They are more like the siblings, the friends you made in the neighborhood where you grew up. Most left the neighborhood at some point while some stayed back. We talked about childhood, about the good old times, the scary courses and the fun professors, our anxieties about not being able to finish the degree, and so on.
The new department: Perhaps the future in-laws, the husband being the new position. The head of my future family (the dean) introduced me to everyone, bought me drinks, and told me how excited they are to have me. I am more like the new bride.
People from the current workplace are more like members from the current family. Yes, I will change families soon, but it is more of an amicable separation.
People who do similar work in the field. They are the potential future collaborators. People I might be developing intimate (academic) relationships with in the future. Academia is interesting that way. Once wedded, you are encouraged to go develop partnerships with others in the field.
And this is perhaps the most interesting one. I was standing with a group of people in the elevator when I saw a familiar face. I looked at the name tag, and I knew who it was. The person never recognized me, but I did, and involuntarily took a few steps backward in the elevator. A person who had interviewed me on Skype, but neither gave me a job, nor informed me about their decision. It was the ex. Someone you had wanted to be with in the past, someone who had rejected you, broken your heart. It might have disturbed me to bump into an ex just like that under ordinary circumstances, but now that I have recently made a new family, I felt like doing a happy dance inside my head in front of them.