Bitfinex

iFinex has run Bitfinex since 2012. The same group operates Tether. The wallets are not the same.

Bitfinex opened in 2012 as a peer-to-peer bitcoin desk and grew into a full exchange. iFinex runs it. The company is registered in the British Virgin Islands and says it is regulated in El Salvador. In August 2016 thieves took about 120,000 bitcoin from the platform. The exchange socialised the loss across accounts and later paid it back in a token.