Thanks for the feedback. If you could send me the details, I'll check that they make sense. The key part is "everything else being equal". The everything else actually influences how important the idea is and how much the developer would get...

2-3% is an entire team lead role; it's what you'd give to an amazing VP/Marketing, or one of your best developers 9 months in.

There may be ideas worth an equity bump, but I think Spolsky is dead-on about the common case: the idea doesn't mean anything. Sure, you can take your idea and work it with another team --- but your prospective team can take their ability to execute and work it on another idea.

Moreover, in many many companies, the key idea that enables the business comes long after the team starts on the first idea; maybe it's a pivot, maybe it's a refinement, but either way, the core intellectual kernel that "makes" the business isn't predictable. When it comes, most teams don't suddenly grant the person who generated it another 3% of the company.

It's destructive to suggest that, in the common case, an idea is worth multiple percentage points. Just zero that line out in your calculator. You can't calculate the uncommon cases, so what's useful is a shared understanding of what "usual" is.

Personally --- again, this is just me --- if you all start at the same time, and you all quit your jobs, and you all get the same kind of income (steady salary, quarterly distro, nothing, &c), you split the thing up evenly. Not even worth discussing. 33/33/33 and vest.