Demographics on Bitcoin users?
I can't think of any known data about real demographics.

But here are some things you can consider to get an idea:


BitcoinCharts' currency distribution: Gives you a view on what currencies are traded the most, most currencies are country- or region-specific so this can be a measure.
BlockChain.info's real-time transaction mapping: You can literally see every new transmitted transaction appear on the map. (This is possible because all transactions are public and have an IP bound to them. But note that some users might use Bitcoin with tools like Tor so their location can be wrong.)