[jauer]

WhatsApp ran on bare metal in SoftLayer prior to (and well after) being acquired by FB.

CloudFlare went well beyond leasing servers and built their own POPs with network etc prior to IPO. Much of what they built wouldn't have made economic sense with AWS tax.

[derefr]

I didn't mean to imply that IPOing is the point at which a start-up becomes a not-start-up. None of these three were a start-up for quite a few years before their IPO, either.