[hn_throwaway_99]

I've also seen cases where pretty well-funded startups (and, honestly, not just startups, I've also seen this with large public companies) have tons of expenses flow through a founder's/upper level exec's personal credit card. The expenses are all legit, but this results in at minimum multi tens of thousands of dollars in credit card bonus points accruing to the exec.

Will let you decide how ethical that is (or not). After all, many/most companies allow their employees to keep points earned for business travel. But it's one thing for an employee to keep bonus points for expenses they themselves incurred, which is very different, I think, than putting tons of corporate-wide business expenses through one person's card.

[merely-unlikely]

As a counterpoint, the founder is effectively providing financing via revolving credit line to the co in this scenario (which the consumer bank issuing the card might not appreciate, but that’s another topic). You mention well funded startups but it’s also common among small businesses for the owner to use personal credit cards (at their own risk) when the business is having cash flow issues.