This is useful to the degree you look for work or workers who are friends of friends, creating other referrals. SixDegrees works like this a little but is not integrated with other services for this purpose. You may see a Relevancy Blending Service emerge to combine scores from several Relevancy services. Relevancy services compete on the quality of their rankings, reflecting specialized knowledge and intellectual property. A service that provides some degree of confidence or trust rating of descriptive data.
Staffing agencies check and test candidates, one of the key differences from job boards.
It might also include any other service employers want, are willing to pay for, or may be legally performed. These services emerged in an offline world. Some of these firms are partly or fully webbifying compliance and validation services. These services are intrusive, especially for a candidate. Certification Authority and Data Validation Services will compete on the normal variety, speed, certitude, and price combination of their services.