Public-Cloud-Appropriate and Public-Cloud-Inappropriate Apps
Just because you can, doesn't mean you should. Some apps are a natural fit for the public cloud; others, most-definitely, are not.
VirusTotal is a great example of a public-cloud-appropriate app.
Confidential/propriatary data in the public cloud? Nope. You have to decrypt the data to use/modify the data, so CloudCorp X can copy that data.
Company-critical app, e.g., payroll? If the mainframe/mini/PC you run payroll on breaks, your service contract (you do have critical-system service contracts with SLAs, right?) gets you techs on-site in an hour to fix it. If a public cloud, or some part of the Internet breaks, you can have techs fixing it in ... ehhh, who-knows-how-long?
"The Internet" does not come with an SLA.