We have a requirement that certain source code are visible by only certain individuals or groups members. Unfortunately snippets only allows us to enable or disable two levels of permissions. We can enable/disable public viewing and enable/disable the visibility of a snippet. If someone with a Bitbucket account has the URL to a snippet they can view it.
Overall we think Snippets is a great way to share bits of code for discussion or as samples.
We are evaluating Snippets and without the ability to protect access to a snippet I'm not sure if we can use it.
Having a User and Group permission setting similar to what can be done with a repo or project would make this ideal for us.