An Early Adopter is someone who:
...embraces new technology before most other people do. Early adopters tend to buy or try out new hardware items and programs, and new versions of existing programs, sooner than most of their peers... [whatis.com]
Apparently Early Adopters could make up nearly 14% of the population. That's a large portion of people who can make a difference. Being able to capture this market is critical to eventually gaining full market penetration.
A number of companies do this in the software space by releasing beta versions at no cost (apart from downloading it). This removes a barrier for people to try the product out at limited risk. In some cases it makes sense to piggy-back on a ubiquitous technology (or channel) to get access to the adopter.
I think that once you stray into making the early adopter pay, especially before they can receive any value, the percentage will dip. What sort of advertising, arm-twisting, pleading can get you to be an adopter?