A the risk of being labelled with the 'tin-hat' moniker I point out that certain bodies, like accounting, engineering, legal, and medical practices, insurance firms, and various levels of government, all have highly personal data on many individuals that has extreme commercial, social, and political value to various actors. Placing ones confidence in the ethics of Google, MicroSoft, Amazon, or any other third party to refrain from taking advantage of possessing ones data on hosts to which their employees have physical access seems to me to be, shall I say, extremely problematic. One does not need an external threat to be seriously compromised.
Open-source development aside I see no good reason to trust github, gmail, gitlab, hotmail, etc., or any 'cloud' based service with personal or client or technical information of any sort. I see an awful amount of risk being taken by people who use these services without much consideration respecting the lack of legal protection or government enforcement capabilities for what little protection does exist.