It's hard to know what a specific company's policies will be, but in general I expect larger companies to still be willing to work with you in the future even i

It's hard to know what a specific company's policies will be, but in general I expect larger companies to still be willing to work with you in the future even if you bail on them. Facebook probably didn't even allocate you to a specific team, so no-one is even expecting you, they're just expecting to need X entry-level SWEs next year. Smaller companies are more likely to take things personally.