I have a team member who refuses to use any form of private source code repository on Github or Bitbucket due to security concerns.  As a result, we have a hard time sharing code with him.  He appears to be concerned about source code theft by some party.  To me, using cloud based source code repos is fairly standard industry practice.  But does this individual have a point?  Vendors do steal from customers in other industries.  Should a multimillion dollar idea not be stored on a third party cloud service like AWS, Github, Bitbucket, App Engine, etc?
Is storing software in the cloud with reputable vendors secure?
version control;closed source
I agree with @david.pfx that a team member has no business in unilaterally deciding for or against a company's business decision, especially as the code is not his... He might raise his concerns, present his case, and let the decision makers (source control may be a decision taken as high as VP or as low as team leader, depending on company policy) accept or reject it. After which - he should accept the verdict.When companies add private repositories on GitHub, they subscribe to GitHub under its privacy policy, which is legally binding to GitHub.As for security, you could point him to GitHub's article on the subject:We know your code is extremely important to you and your business, and  we're very protective of it. After all, GitHub's code is hosted on  GitHub, too!They go on, and detail the security measures they take physically, operationally, etc. and also address employee access.At the end of the day, you must trust someone... servers may be compromised, third party libraries may contain malicious code, and employees may leak information or sabotage the product - but without trusting (vetted) servers, libraries or employees - you would achieve nothing...