One or Multiple Vaults?

Dear Forum, 

During a conversation with another M-Files user, one feedback I took note of was the comment that companies should never operate just one vault.

Their feeling was also that HR (due to its sensitive data) should also be excluded from the main vault.

My understanding is that the comprehensive security including NACL's means that any sensitive data can be managed effectively if placed in one vault.

My question for others is:

  1. In which scenarios would you operate a second vault / or in what scenarios would multiple vaults be beneficial? (aside from a publishing vault) 
  2. Are there any major risks of operating one main productive vault that we should be aware of?
  3. Is there such a thing as "best practice" when it comes to vault operations and management. 

Thanks in advance for your feedback