The 600 million numbers that Truecaller has in its directory have been collected via crowd-sourcing. Truecaller’s users can share their contacts and in return they get access to search in the collaborative database. Thanks to this collaborative data solution, the directory is growing and being updated continuously. It also contains numbers that no other directories have, e.g. pre-paid phones.
It's clear by the running total on the ProgrammableWeb homepage that there are a lot of APIs. In addition to a lot of companies with APIs, there are companies with a lot of APIs. Google has the most--surprised? You may be at some others than make the list, from social networks to online marketplaces.
ALFAcashier has opened an API for access to its electronic currency exchange and associated features. The API allows users to integrate cyrptocurrency exchange functionality directly within third party sites and apps. Additional services include order creation/status/tracking and address validation.