"We expect more traffic, the number of unique users to go up... an increase in audience engagement and more repeat visits," which in turn will drive advertising income, said Mr Riley.

Many personal stories confirm the hypothesis that once we experience deep engagement, it is a state we long for, remember, and want to repeat.

However, the likelihood of repeat sales depends on Blue Nile's ability to deliver a truly memorable experience to those customers who first purchase an engagement ring from the web site.