Cost per click was more common in the early days of affiliate marketing but has diminished in use over time due to click fraud issues very similar to the click fraud issues modern search engines are facing today. Contextual advertising programs are not considered in the statistic pertaining to the diminished use of cost per click, as it is uncertain if contextual advertising can be considered affiliate marketing.
Dropbox’s referral program is perhaps the most familiar example. Refer your friend to Dropbox, and both you and your friend get extra storage. They could afford to do this, presumably because the additional cost of a little extra storage was minimal compared to advertising costs or other means of customer acquisition. It benefited from network effects, too: the more users there are, the more users will use it together. That entrenches the product and service in popular psyche.
However, labelling such marketing as referral marketing isn’t very meaningful- anybody can tell anybody to tell everyone else about their stuff, and good stuff gets shared all the time, sometimes even if the originator asks for it to kept secret! It’s a lot more meaningful to save the “referral marketing” label primarily for distinct, deliberately solicited referrals.
Apart from looking for particular niches and individual affiliate offers, it makes sense to consider affiliate networks – aggregators that allow the publishers to manage multiple offers and get commissions from a single place, while removing the hassle for the advertisers of setting up their own programs. Below are some of the most affiliate networks: