I work in legaltech, and we use cloud services like aws for lawsuit data, and lawyers trust it. Any 3rd party must of course be vetted and go through NDA, and follow regional laws and guidelines ect, but using the cloud is definitely used for legaltech documents including sensitive data.
It should be added that legaltech vendors are often employed as go-betweens for quite adversarial interactions, such as e-discovery, that require them to be trusted (to a degree) by both sides of a case, even if they are being paid by one side.
Seems like there are lots of confidentiality and reliability issues in how tech is being used in law right now, but there aren't that many attorneys who understand the issues, and those that do find it more advantageous to overlook them unless forced to do otherwise.
