This post helps you to disable the My Site Link that is at the top of SharePoint site based on the rights of logged in user.
Open the Shared Services Administration Link from the Central Administration page.
In the Manage shared service page select the shared service to which your site for which you need to manage the My Site Link is mapped.In the below fig I am trying to manage My Site Link for Site SharePoint - 6000,So I am selecting the SharedServices1.
In the Shared Admin page select the link Personalization Services Permissions Link present in the User Profiles and My Sites Section.
Select the user group for which you want to enable or disable the My Site Link Permission.
Check or Uncheck the Create Personal Site Check box to Manage the Rights