It’s common practice to throw up a free download as a way to build an email list ail list bait to lure subscribers to your list.
I typically do not build my list of emails for marketing that way because I want to maintain a high quality list with people that are potentially serious about becoming customers. As a result, I do not use free downloads as bait. In fact, I do not promote my list at all in the overt, in your face ways like popups. Instead, I subtly offer the availability of my list in a discrete ad in my posts, with the subscription form at the footer of the page.
Once I get a prospect on my list, I have a series of autoresponders with mostly helpful content that ties back to what I sell. In those emails, I offer free access to content or additional downloads, but I don’t just serve it up. Instead, I am funneling clicks to an actual product that is for sale on my website, but which I have discounted to $0.
The customer can get that product for free, but they must go through my checkout process. In this way, I am getting a physical address for snail mail campaigns, and have the option to use their address to obtain demographic data that I get from third party providers. I am also forcing them into my sales funnel, so I can attempt to upsell them on a paid product or two. I might start with a really cheap product like a trip wire.
Does all this reduce my list signup and people taking my free content? Of course, but with these strategies, I know I get more high quality leads.