Q: How do I control who is allowed to create My Sites?

A: By using "Manage User Permissions" in the User Profile Service Application administration tool. The default is that all users get the "Create Personal Site" permission. To change this, remove "Authenticated Users" and "All Authenticated Users" from this permission and add the AD global groups to which you want to grant the permission. This blog post from SharePoint expert Dave Coleman gives the details: Locking Down My Site SharePoint 2010 - SharePointEduTech