So as example they sign up in an opt in form then they sign up to another or more frequently they are signed up to another offer, yours as example, cause there's the permission to give the lead to third parties.
Often it's said that with a good funnell and follow up, they can be good.
Obviously they are very cheap in cost,
I did a test but these leads were really crap.
Anyone has any positive experience? Do you use it? What are the companies do you raccomend?