In what could be boon or bust to PR agencies, LinkedIn now has a Companies tool in Beta that allows you to see in one screen who tends to connect with whom, and which direction the Revolving Door tends to spin.

Currently 1,675 public relations companies are identified, but the data isn't altogether perfect. It depends on how users enter their information. For example, Ketchum is listed as Ketchum PR, Ketchum Public Relations, and just Ketchum--with three different company descriptions. When you click through each, the page tells you the people you're connected to at the company and the degree of separation. Descriptions are provided by Capital I.Q., a division of Standard & Poor's by way of BusinessWeek.com.

What's fascinating is the Career Path tab on the right side of the page that shows where people tend to come from, and where they tend to go. I'm only using large firms (1001 - 5000 people) as examples because of the larger data set.

Edelman people come from Burson-Marsteller. Burson-Marsteller people come from Edelman. And both go to Weber Shandwick. Draw what conclusions you will. This is however, an opportunity for agencies to promote themselves in an era of heavy competition for clients, and for talent unwilling to make a career switch in a tough market.

Related: "Tip: Use LinkedIn to Calculate Turnover"