Hiya! It turns out there's a lot of thought and discussion and beating around the bush about these ideas. In fact, I came to this forum by landing on this thread: http://forum.bitcoin.org/index.php?topic=3176.0
which eventually drifts into a debate about exchanges, the points where the BitCoin economy intersects with the government-sanctioned economies.
One great read (also mentioned in the thread) is: Toward A Private Digital Economy -Trusted transactions in an anonymous worldhttp://pelagic.wavyhill.xsmail.com/Private_Digital_Economy.html
Especially, see the section about Ghost Walkers http://pelagic.wavyhill.xsmail.com/Private_Digital_Economy.html#Ghost%20Walker"
who function as anonymous micro-exchanges
There's also a nice post listing news stories of non-sanctioned exchanges that have been shut down: http://forum.bitcoin.org/index.php?topic=3176.msg45198#msg45198
Thought-provoking stuff. I'm surprised there's not more discussion about these concepts here in the Newbies section.
Do you have experience dealing with a LETS ? It seems like a perfect use for BitCoin, both within a LETS and perhaps between LETS(s).