Honest questions: what percentage of Paypal's revenue comes from eBay? Is Stripe's pricing model unsustainable at the lower tiers? In other words, what's stopping them from serving millions of small merchants instead of a few giant ones?
Paypal/eBay - couldn't find any published figures on this, but looking at eBay's revenues vs. PayPal's revenues, it'd appear that it's a substantial but not dominant share of their revenue.
Pricing model - no, it's great, but as you grow, it becomes uneconomical.
What's stopping them? Fraud. Fraud fraud fraud. They will end up with an approval process, as if they get hit big a few times (they will), their merchant acquirers/clearers will insist on it.
