4 Expert Insights

A couple thoughts.  First someone needs to have a conversation with this young man, and quickly.  Second, how did he know that there were boundaries?  Was the protocol that you're describing formal or informal?    Regardless, he needs to be clearly told.

After you clearly define the protocol, I would carefully observe how he responds.  You describe him as smart and ambitious.  I would question smart, if he did what you described. Ambitious yes.  I would reflect a bit on his actions and assets in terms of how he responds to the feedback.  If he is smart, hopefully, he will accept the correction and act appropriately.  I would watch your 6, though to make sure the ambition isn't stronger than the smart.

I don't know much about your organization, size or industry, but suggest you give some thought to a new hire assimilation plan where you provide a context for the new hire to understand protocol, understand what is important in the job, and set a learning plan for the first several months.  This structured but informal method allows for learning on the job, and through mentoring.

Most people love the notion of having some autonomy in their work, and many organizations recognize the value of having people do what needs doing, rather than waiting to be told what to do. Autonomy must be coupled with accountability, however, in order to keep work efforts aligned with organizational mission, values, and strategy.

Your new hire has done some things that were out of line. Some of it may have been simply naiveté, but some of it may have been the result of having to figure out boundaries on his own. He doesn't need a public shaming, but he does need feedback. A flat organization has fewer bosses, but it probably needs more mentors. A mentoring relationship with your new hire would allow not only feedback on faux pas, but setting appropriate expectations re his role and behaviors, while developing his potential by building on his strengths.

I certainly agree with Bill's answer above.. regarding the importance of assigning a "mentor" to this new hire.
It would be critically important in this case.
The company should do so, as a matter of course, also as a component of a more formalized "on-boarding" program that starts upon acceptance of the letter of offer, and continues not for days.. but for Months beyond the new hire date, making sure the new staff member is fully engaged, exciteds to work there, understands his role, the expectations of his management, the resourece available to him to do his job, and importantly, gain an understanding of the culture and policies, mission and vision of his new company.

We all are advocating the mentoring concept, caveat being that the mentor is teaching the right behaviors.