I've (co-)organized parties of varying sizes (N=2..50+) and I would say volume hasn't been the top problem, ever.

- As hosts, the main problems are finding a suitable date to hold the party, chasing attendance confirmations and getting people to dance (esp. once they're over 30).

- As attendees, the main problem besides whether on should go or not (which is often made dependent on who else is going) is figuring out what kind of "party" exactly it is (formal/informal, dance party/potluck, enough food?). The definition of "party" is very broad, even leaving aside cross-cultural norms, ranging from "let's sit around the table and play board games" to "let's outdo Hangover I/II/III [except for the giraffe]".