We've been plagued by one or two of these a lot of late - one even claiming that "someone" from our company registered us on the site, because they never would take it on themselves to cold call.......yeah right.
As most have found, they look for a certain "commitment" from you - in the form of paying for leads, a lot like you'd pay for a mailing list, which IMHO would be of statistically greater value. The costs of £9. £15, or £30 (I think) per lead, work out very expensive next to many other methods, when you consider, £30 a "big" lead, three times a week for a month is roughly £400 a month.
You could do a lot of damage of Google Adwords for that kind of money, with a very simple campaign, and probably generate a far better return.
I'm not at all convinced by any of them - and even less so when if you challenge them, they're not prepared to back their services in any way at all with a trial of any type - we asked them for a month of free leads, effectively to pay for six months further leads, which we would have committed to had the leads been of a quality we could use.....they were not at all interested.
Why wouldn't you put your faith in your service like that? Seemed like a win-win deal to me. Unless they had something to hide about the quality of their lead generation.
I also can't see with most of them exactly how they guarantee trades suppliers are of better quality than anyone else not on their service, or convince potential customers that the "few" are the ones to go with.
It does seem to me to be a scam from both directions - however, I will say that in principle, the idea of a "recommended" trader service would be a good idea, but for human nature. Most of these lead companies, are only there to make money, and they don't really care how, so long as they can bill for something.