That 250,000 figure might not be correct. The truth is we don't know exactly how many Bitcoin users there are but there are indications that the number is higher than 250,000. Freebitco.in has over 1 million accounts. Coinbase alone has over 2 million wallets despite only being available in 19 countries (and even less a few months ago). Since they also implement AML/KYC laws, it would be rather unlikely for users to have multiple wallets there. Blockchain.info has 3 million wallets.
I've seen estimates ranging from 250,000 to as high as 10 million:
"Bitcoin has this promise of enabling innovation. There are already 10 million people or more using bitcoin."
Link: http://www.coindesk.com/bitcoin-stellar-sidechains-feature-future-money-summit/
The true number is probably somewhere in between the two extremes.