Here is my first-cut checklist. Please chime in. Incomplete profiles are either worthless, less valuable, or add noise to search results. Of the fields required to perform a minimu skills match, what percent of the records have this information complete. It is useful to understand the requirements of each type of user.
Most labor markets remain local.
To accomplish a balance between workers and jobs, both must reach a minimum critical mass in a given territory. As people move or change jobs, email addresses often change. Will a human reply to an inquiry with sufficient incentive. Stale data may be worse than no-data. Bidirectional filtering for mutual fits.