Email, which is one of the oldest services available on the internet, is a key mechanism via which you can reach out to your users. Over the last year, the number of services providing this infrastructure as a service has grown to include 6 email sending APIs. The newest, Amazon Simple Email Service, validates the market.
An email address can be the key to an online identity, and that's just what IDLight is using in its identity lookup API. By supplying either an email address or a URL to the IDLight API you could be turning the key to unlock a swath of identity information.