Twitter recently disclosed an "incident" in how the service handles phone numbers. The announcement declared that it had shut down "a large network of fake accounts" responsible for uploading lists of phone numbers and then using Twitter's own API to match them to individual usernames.
According to the Electronic Frontier Foundation (EFF), this is precisely the type of activity used to create reverse-lookup tools: the types of services that match specific users, or their accounts, with an otherwise random phone number.
