[patio11]

I am guessing, and patio11 can back me up if he agrees, that it is much harder to get a teacher to your site in a cost effective manner and then get them to pay than it is to write an application that randomizes a set of words and prints them out.

It is harder to get a couple hundred thousand teachers on your site than to write an application. It isn't terribly difficult to get a couple of hundred on the site, or a couple dozen to use the application, or a couple to use the application with you staring over their shoulder.

I particularly like organic SEO / AdWords as early channels, because if you can prove they work in microscale, they typically won't totally break down right after microscale. (Obviously, BCC isn't going to Facebook scales.) i.e. if you can reliably turn $1 into $2 you can probably turn $1,000 into > $1,000.