I particularly like the pie calculation as it addresses more variables more effectively. I would add that the agreement used (probably an LLC or Limited Partnership rather than a corporation) should provide sufficient flexibility that when things change (and they certainly will) the agreement is ready to help adjust the relationships. Thus, I would, among other things, use the pie chart each year to help adjust the relationships to meet changes that have happened over the year. The prime example is the founder who left after six months to do something else. Or the manager who is brought in after the idea is making money, but not much money.
The whole point of Joel is that you want to avoid addressing those variables because it leads to arguments. It's impossible to determine almost any variable without being subjective so you open the door to fights. The only non-subjective way is an equal split.
