Pretty vague question.
SELinux is very effective at controlling what a process can do, and mitigating bugs in applications. In any multi-tenant environment, I would not run a system without SELinux protection. Secure Virtualization with libvirt and VM's relies on SELinux. Openshift Relies on SELinux. Tools like Secure Containes also rely on SELinux for protection.
You can read lots of information about SELinux on my blog danwalsh.livejournal.com