Turning "Visitors" into "Loyal Evangelists" is Impossible.

The verb turning implies that you actually turn something.  I believe it is impossible to "turn" a visitor of your website/store/product/service into a "Loyal" evangelist.  It is hubris to believe that we caused a "turning" to happen on a person.  So, instead, we must console ourselves by giving our visitors/customers every possible reason to decide to turn themselves!  Here is a short-list of things I've tried to "turn" visitors into evangelists.... and the success thereof.

1. Make the website/app look good.   Result: fail.  Opinion: good looks are not enough... they are expected.
2. Make the website/app easy to use.  Result: helps.  Opinion: combined with good looks... it is definately a "reason" someone might turn themselves into an evangelist.
3. Cheap Rewards.  result: fail.  Opinion: cheap rewards (such as useless points, etc.) are not effective.
4. Expensive Rewards.  result: so-so.  Opinion: if combined with other "reasons" it can push some % of visitors/customers over the edge.  *See loyalty cards.
5. Charity involvement: result: fail.  Opinion: Charity connections really don't motivate like they used to.
6. Delight the customer... underpromise, overdeliver.  result: WIN.  Opinion.. if there is ever any reason that a person might have to "turn" themselves into a loyal evangelist... this is the one.

An anecdote: I am a fanatic about Audible.com.  I use it for 2 hours every day (on my drive to/from work, I listen to books).  It's super easy to use website is reasonably attractive, and never fails me.  I always find new books I want to read, and the simplicity of sending them to my iPhone is delightful.  I am a delighted Audible fan, and for that reason (and maybe a few others), I am a loyal evangelist for audible.

The question: how can a Marketing Company (like Karmaback) help other companies DELIGHT their customers?  (and how can we measure it)?