Progressive engagement vs Direct call to action

Most websites that sell something (products or services) use a direct call to action.  Here's my product.  Buy it now!

Direct calls to action aren't bad, but along with the content revolution, many consultants are advising companies to use progressive engagement.

The concept behind progressive engagement is simple.  Instead of asking for a bunch of information upfront, you get a little bit with the first engagement, and then progressively collect more as the consumer's trust in your company presumably increases.

Here is an example of only collecting an email with the free "intro" ebook, and collecting additional information when the same user tries to download the "advanced" ebook.

Progressive engagement is designed to capture and track potential customers who are still in the discovery and evaluation phases of the traditional sales cycle. (Discovery → Evaluation → Purchase)  Direct calls to action only focus on purchases.  

I think progressive engagement is a great way to see who's interested, determine their current stage in the sales cycle, and measure their commitment and trust.  BUT, with that being said, you can't abandon your direct calls to action.  

Your website visitors are all in different stages of the sales cycle and have different purchasing habits.  Some need a longer, much longer, runway than others, and some have been waiting for years to find someone like you.  If you fail to have a direct call to action, it is the digital equivalent of slipping into the friends zone.

If you don't ask for the sale, they'll end up asking you for advice about another company.