You may come accross the requirment where you would want only certain group of people to be able to create my sites. This is possible by modifying permissions on Shared Services Provider, to do so follow these steps
1. Logon to Central Admin
2. Click on the Shared Services Provider that hosts my sites
3. Click on "Personalization services permissions" under the group "User Profiles and My Sites"
4. Click on the group "NT AUTHORITY\Authenticated Users" if it exists in that list and untick the option "Create Personal Site" and click save.
5. Using the menu on the permissions page, add the SharePoint group that you want to give permissions to
6. Click on the Group that you just added and select the permissions "Create Personal Site" and jobs done!