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.
Of course I had to try this out on myself. When I entered my own gmail account I was reminded that I've had an abandoned flickr account sitting around when I saw its URL in the JSON formatted API results. I was a little more pleased with the results from searching with my twitter profile URL. A few more relevant links were returned in that result set.
How did I test the API so quickly? IDLight has provided two places in which to investigate their API. First, theirs the Apigee developer console for the API right on IDLight.net. Second, the API is listed on Mashape where you can also find a nice developer console.
This is a free service, that looks to be the creation of a single consultant. He's taken the modest approach of only billing if a serious API user appears. Currently there's more than 30 identity APIs in the index, but just a few are enriching identity data (such as emails and URLs).