heh. excellent question. "in charge" is relative. most of the time it seems pretty automatic, which is nice, for sure.
technically (not technologically) speaking, ed stastny (id OED) is the primary maintainer/coordinator/braintrust/janitor. i do a lot of the programming and share some of the day-to-day stuff with ed. there are lots of other sitoans who have (and do) volunteered time to help out in many ways.
ed and i are portland oregon, the server lives in omaha; but sito comes from the hearts and brains of many artists and helpers! (ok, thats a little cheesy.)
when i really think about it, it all seems a little tenuous ... so thats probably why i dont think about it much.
aside: this would probably make a good bullet point for the non-existent sito faq. or, at minimum, should be in the help files somewhere.
(and thanks SO much for the praise and for recommending sito!)
update: i have made a help entry on "who is sito?" to at least begin to address this stuff.