Trail Families

One thing you have on the AT are trail families. While most people start the hike on their own, they rarely hike the whole way on their own. Sometimes you meet up with one person and hike with them for a couple of days, other times you get together with a whole group and spend several months with them.
They are many advantages to hiking in a group. When you get into a town you can split a shuttle or a hotel room several ways and make it more affordable. Also if something goes wrong while in the woods you have multiple people to help you out. You also have a support network of people who are keeping you motivated and on trail. You also then have a wider network of contacts for places to stay along the trail.
Trail families tend to be fairly fluid. Since you did not start the trail together there is not as much pressure to finish together. If people have different speeds or different needs, they do not have to stay together. However it gets harder and harder to enter a trail family as you go further. Some tend to close up once they have formed, or you have people who have hiked together for months and no matter what an additional person will feel like an outsider.
Some families take on names, I have been in the Kielbasa Klub at one point and I am currently in Aggressive Male Nudity (Amen). A friend who hike last year was in the Iron Chefs (because of their cooking skills), and currently on trail we have the 4 Sisters, The Invisible Hillbillies, The Pain Train and The Main train to name a few.