I actually think they are mediocre at best a lot of the time, though Buzzstream is the best and is building out a solid database. I usually personally use Mecha

I actually think they are mediocre at best a lot of the time, though Buzzstream is the best and is building out a solid database. I usually personally use Mechanical Turk to find the real email addresses, but some human rights group got bothered that I would recommend a service that doesn't provide a living wage and gave me hell for two years. So I took that part out publicly, but it's still in the book version.