1) Here is a list https://99bitcoins.com/who-accepts-bitcoins-payment-companies-stores-take-bitcoins/ https://99bitcoins.com/who-accepts-bitcoins-payment-compan

1) Here is a list https://99bitcoins.com/who-accepts-bitcoins-payment-companies-stores-take-bitcoins/ https://99bitcoins.com/who-accepts-bitcoins-payment-companie... -- a lot of stores indirectly accept bitcoin via payment providers like bitpay.com, but I could not find a list. 2) Hard to tell because of (3). But you can approximate it using the exchange volumes: https://bitcoinaverage.com/ https://bitcoinaverage.com/ 3) Unless you are doing a targeted search, mapping an individual to one of his addresses, it is very difficult to run an analysis. This makes it hard to answer (2). It successfully used for illegal activities.