Cooperation is dandy if n = 2, but for n > 2, this can get cumbersome. Unfortunately method names like 'sum' are very attractive.

A language/library designer shouldn't have to think of "all of the short or otherwise possibly overloaded nouns and verbs people might like to use, ever." Being able to say you are going to do a 'sum' which means X in this particular context is very powerful.

This notion should also be unified with version control. (As in OS X, where a process only sees the versions of libraries that it is supposed to run against.)