I think it's safer to assume HassleHoff is right about the record keeping and all, but I don't see it as likely that just people who are involved with bitcoin software & the network have tabs kept on them. BTC to USD and USD to BTC transfers, I have no doubt about. But not just the software and stuff. There's a big bitcoin community. I mean seriously, some people are almost religious fanatics about the whole Bitcoin ecosystem. For example, I love this one thread, it's hilarious and wonderful at the same time -- https://bitcointalk.org/index.php?topic=12156.0