I think this is a great idea...shame I'm nowhere near.
I generally think that long distance athletes gather in groups for the following reasons:
1. They get bored due to the low level workload and like to have others to talk to.
2. Wearing lycra and the other horrible fashion they endure feels better when there are lots of you wearing the same thing.
3. In Paleolithic times, the weak and skinny had to band together for safety.