I am not suggesting people form corporations as a first step, only that they come to a general consensus on equity and commitment as early as possible. Personally, I've had long discussions with potential cofounders who suggest exactly what you say, and when pushed they offer 2% because they are the great idea and execution genius who can pull funding. All those people failed to find competent partners or raise money.

Had these founders not had an agreement, corporation or not, the founders who left would continue to have a very substantive claim on the business as part of the partnership.

You can read here about what happened in one case when this went wrong:

http://www.milwaukee-business-lawyer.com/what-happens-when-o...

Courts hold that a partner who leaves a business lacking an agreement does not lose rights to their portion of the business. If it can be proven that there is absolutely no relationship between the old and new product, perhaps it could be shown that a new partnership was created. This is not a lawsuit you want to deal with.

That is why pretty much anyone giving competent advice instructs partners to decide how they should split equity and on a vesting agreement ASAP. That doesn't mean these agreements can't be changed as commitments and roles evolve, but the existence of an agreement makes those conversations necessary. Without one, fundamental disagreements often lurk.

Over and out.