Not sure I entirely agree with this. For any sizeable niche (or even smaller niches) you should be able to find places where these people hang out on line and get in touch with them. If you can't then you don't know your target audience well enough.
You could certainly use advertising to collect email addresses, and then call those people to figure out what they want. The reason I don't like that as much is it puts another layer of specialized skill between you and your prospects. You have to dump a bunch of money and time in to learning how to write correctly targeted ads that convert before you even know who you're trying to convert, or what they care about. That's a tough problem to get around for most people.
You could certainly use advertising to collect email addresses, and then call those people to figure out what they want. The reason I don't like that as much is it puts another layer of specialized skill between you and your prospects. You have to dump a bunch of money and time in to learning how to write correctly targeted ads that convert before you even know who you're trying to convert, or what they care about. That's a tough problem to get around for most people.