Is it possible for two or more people to access their own individual iTunes library on one computer?
Is it possible for people to share a computer and be able for each to access their own personal iTunes accounts?
iPad 2
Yes... accessing the account is easy, simply log in with the account you want.
If you want to be able to access the media, that is different. The media must be physically on the system.
Please provide more detail of what you are trying to accomplish so we can offer assistance.