Do you want to integrate webcenter with EBS? If you want to install stand alone webcenter portal and do not integrate with EBS, then there is no need to integrate OID. You can work with static users defined at WC level for demo purpose.
Go through the below MOS Notes
Using WebCenter 11.1.1 with Oracle E-Business Suite Release 12 (Doc ID 1074345.1)
This document says that you need OAM/OID if you want integrate EBS with WCP
If you need to log in seamlesly to Webcenter using your EBS credentials you wll need to setup OID as the Identity Store and OAM as your Single Sign On engine.
What Rohan said makes sense .. if you just want to install without doing anything you won't need it.
Having said that its definitely not a quick install !
Thank you all for your replies, and I can see now that I'm going to need to go down the OID/OAM route. It's a shame that the EBS doesn't support OUD yet, as it will be easier when we can use the Oracle Identity and Access Management Deployment Wizard!!