It is common and sometimes known as 'fleecing'. Recruitment consultants will phone up a contractor/freelancer and try and glean knowledge of large companies who are hiring. Then they'll put together some cv's on their books, contact the company and try and make a placement. Often this will happen with companies that the recruitment consultant wants to get new work with. Ideally as a preferred supplier.
Sometimes the recruitment consultant will call a contractor/freelancer and tell them that they have a great position but can't tell them as it's a hot contract, instead they ask the contractor/freelancer all the places that they've applied to/interviewed at in the last week/month, then they say that the hot contract was one of those on the list that the contractor/freelancer said. (That way they get to know all of the places currently hiring).
Recruitment is often a low salary with a high percentage on placements made... Often the environment is fairly cut throat with
alot of pressure to place candidates... I guess ethics are a little shaky in such an environment. I tried it for a short time about ten years ago but find that I prefer the other side of the
fence.