1: Mark Zuckerberg wasn't a particularly social guy, so his founders/product fit was 0.
2. product/market fit: Facebook was a social network just for schools, this doesn't really show any product/market fit. it's a super niche product with no obvious revenue model.
3. founder had zero social proof. couldn't even bag any advertising clients.
4. founder didn't get along great with team, in fact all team members sued him.
5. the very first verison of the site looked and features it had in 2004 - https://www.quora.com/What-did-the-first-version-of-Facebook... does not show that much progress or activity.
6. Mark was just a Harvard student, so were the other team members, no dedicated staff at all.
7. No basis to judge.
8. No prior past experience to judge from.
Based on the above there is a 0.00% chance that you would fund Facebook at the seed stage, at any valuation. Out of 8 standards, you would have to give them a 0/8 on nearly all of them.
but hey, the fact that your investment thesis fails with perfect hindsight, doesn't mean it can't succeed when things are a lot more murky. go get 'em.