People! At least that seems to be the obvious answer to me. For what ever reason PM has attracted a critical mass (self substaining etc.) of folks who care enough to be involved on a more than simply passive basis. Having said that it occurs to me that whatever the reason(s), it does look like it is something that attaches to both perl the language and perl the community. The closest similar such is the TeX world, but it isn't anywhere near as comfortable. Much what you would expect with its primarily academic roots. Perhaps pragmatism is a more communal basis?
in reply to Why does PerlMonks work?
"Never try to teach a pig to sing...it wastes your time and it annoys the pig."