Does anyone have any idea how many bitcoin users there are?
If not what would the best way be to find out an average? I would like to see the user growth rate over the next few years if this is at all possible.
Here you can see the number of unique adresses used every day:
http://blockchain.info/charts/n-unique-addressesSome of this may be spam, though, i.e., just random transactions between wallets that are all owned by the same user. But about 50k different wallets are in use every day, it seems.