Before i deal with the points you raise first lets look at the core issue, references themselves. These days these are totally worthless because due to legal issues no one in their right mind dares to give a truely honest one, aka a negative one. If the client does that they risk getting sued.
This in it's self invalidated them from the get go for using them to determine if the contractor is any good as all they are likely to get to is either "sorry we don't give references" or a good one.
Now you could say if you get the former response that you could assume that if they did could give one they would give a bad one, but fact is many companys do really actually have this as a policy as the legal advisors for the company don't trust joe blogs manager not to get the company in legal trouble.
Now sometimes the contractor manages to work around this by becoming very friendly with his/her manager who will do it even though it's against company policy, but fact is this is not longer a world where everyone stays in the same job/position/company for life, hell sometimes a contractors manager is yet another contractor.
This exact situation happened to me a few years ago, 2 years working for same company. Was against company policy to give references but my boss told me before i left would be no problem giveing her name out if i needed references.
Only problem was, 3 months after i left she left the company as well, gone who knows where (she like the entire team was also a contractor and project was over). And there is me left with 2 years work and no reference to show for it (pre typed one i had was useless, anyone could fake one of those). Only thing any agency would get from them was a confirmation that i worked for them for 2 years, and that was it.
So before we even get to the blagging for leads we have totally invalidated the official reasoning behind references.
Now to the blagging by agencts, Few years ago after leaving a contract arranged with my boss to keep track of calls he got from agencys that i had given his details to for references (he had become a good friend).
Now till this point his details were not "out there", no agency ever called him because they did not know he existed as he had only transfered from the states office about 3 months before to over a new department (gave his details to about 20 agencys)
17 of these agencys called him (even though all agreed not to unless the client at least reached the request for interview stage, which which only 4 did, and one of those 4 never did call him)
All gave him a sales pitch (two invited him out to lunch)
Rougly two thirds spent more time on the pitch than actually discussing me (hurt my feelings *crys*)
4 never actually mentioned me again after the initial "X gave us your number"
2 never mentioned me at all.
Since then i have only given reference details out once and that was only when i had the offer and contract right in front of me and even then i refused to give more than one even though they wanted two.
Rather than go to one agent you know well, who is well connected and a bit ruthless about getting you a job, just think of the number of agents there would need to be to cover every snippett, every opportunity that existed on the market.
Honestly, this is how most of the market exists already. Sure there are the CP and CF types that have a particular client here and there in the bag but majority are just latching on to everything and anything they can.
Now imagine that agents were prohibited from coercing information in this way. There would be many many more of us all armed with only tiny (relatively) bits of information, none of us would have a really good knowledge of the market.
In reality most agencys don't seem to have good knowledge of market (especially the large ones) and this is the very reason they are trying to get reference leads out of us. If they did they would not need our leads as they would be out there getting the information for themselves, via marketing, networking and research and then building up good relationships with the clients.
Asking for refernces does not need to banned, what is needed for contractors to stop playing the agents game and giving them out and probably screwing themselves over doing it. Then once agents cannot get contractors to sign up they will drop the requests for refernces, hell most have already.
