With the market the way it is today, I'm reluctant to pay for any services that don't have some sort of guarantee of service. All of the web sites, including Trulia, that I've found make no guarantee of the quality of the information they provide. The leads aren't vetted, so to me they're useless.
I'd rather pay a 25 percent of my net commission check as a referral fee to someone for a vetted lead than to have what amounts to a cold call that I've paid a fee up front for.
Even Trulia, and their "Pro" service, doesn't give you anything more than somebody who may have expressed some interest in a property. To top it off, they give those leads to several agents at once. And all of the other sites I've run across do the same thing. So what, exactly, are we paying for with services like these?