Not sure what I can really add but, as with most lead gen services, I'm a proponent of try it, see if it's a fit, and if it isn't, move on. Customer acquisition cost is an easy enough number to figure out, and we all know and track those, right?
Of all AL feedback I've received, it seems to entirely come down to the market's population. But, this is the same for just about any lead gen service. It's a straight up game of statistical probability. As Will P.C. mentions, if you live in Chicago, you're going to get requests for landscaping work. If you live in BFE, town of 150, you might have a very looooong wait.
I agree with everything Headz said. Sure, it can be an annoyance, but the verified background outcome can be a great badge to rally (and market) around. Implementing this program, hopefully, helps raise the quality for everyone. Along the way, it might just eliminate some of your competition, too. One only need look at the heavy PR hit that airbnb took
to know that a level of accountability has to be maintained, especially when the home owner is paying AL for the name of [maybe he's a criminal, maybe he's not].