This article is part of the contractorcalculator.co.uk's sales guide for contractors. In this article they describe how recruitment agencies work from a sales perspective. 
"The Role of Recruitment Agencies and How Agencies Work
First and foremost, let’s be clear on one point – a recruitment agency is a ‘sales brokerage’. This means that agencies are run by sales people who are aiming to make a margin on the work you are contracted to do. Whatever you are paid, the agencies are applying a margin on top of this, which is their profit and the reason they are in business!
you can not expect to make the best use of any consultant or agency unless you understand their objectives and processes
agencies do not have to have your best interests at heart
The Agency's Customers
Recruitment agencies have two customers:
- their client (the employer)
- the candidate (the contractor)
Which of the two do you think is more important?
the most important customer for the agency is their client
agencies want to place contractors into positions where they are already qualified.. and have experience
Their role is not to better your career, but to find you, place you quickly, at a profit and to keep your new employer happy. This may be over generalised, but be sure to keep this in mind when positions are being presented to you.
How Your Rate is Determined
How is your rate of pay determined? Well, this is typically negotiated by the recruitment consultant. Their aim is to make you (the contractor) and the client (the employer) happy, as well as making a profit.
In summary, recruitment agencies and consultants are not the ‘necessary evil’ they are sometimes perceived to be. Neither are they working specifically with your best interests in mind. They are a business. As with any other business, if they lie and cheat they will be exposed as doing so at some stage by the contractor and employer alike. If they are reputable and well established, the chances are they will have some interesting opportunities for you."
I do not like to make a subject last for so long as I did with the present one, but I believe the importance of the one hereby developed needed some opinions foreign to this blog, ranging from professionals to common people who, due to their experience on the matter, could offer a realistic idea of the value of recruitment agencies, their ethics and organics. The Toxicologist Today will be back to the main root of this blog, Toxicology and Science Research in the coming weeks, stay tuned. For some more information on who should you trust when looking for advise regarding job hunting, please, follow this particular link that can offer you some extra insight on the agents and individuals you should rely on. Apart from all that just believe yourself, always give your very best and enhance your skills whenever possible, See you soon!
 Contractor calculator, Understanding recruitment agencies and consultants,
http://www.contractorcalculator.co.uk/recruitment_agencies_and_consultants.aspx, last visited on the 20th of April 2011, last update unknown.