1) An account that is a member of a default privileged group present in Windows 2000 through Windows 2003. Has the ability to install random crap and break everything, but not the ability to fix anything (unless they exploit their breakage ability to escalate privileges).
2) Someone who reads "top ten ways to..." articles on sites like Digg, Reddit, or Lifehacker and then blindly copy-pastes shit from <pre> boxes into their terminal. They have no clue how anything works nor the facility to learn, but they sure are earnest and they love to evangelize! They'll seize any opportunity to apply their cargo-cult knowledge to help you with the problems they think you have. They love to defrag and "Repair Permissions", but don't have backups. They're the audience/creators of 'themes' and 'skins'.
Historically these people (largely adolescents) have been know-nothing partisan tweakers of Windows, Classic Mac OS, BeOS, Amiga, or any number of 8-bit home computer platforms. Recently Linux has become the cool thing to wank over -- compiz and Ubuntu helped a lot with that. The Hackintosh phenomenon has led to a lot of them defecting to Mac OS X.
Of course the person is limited. They are limited because they can't for example, install Firefox on the iPad and use it as the browser rather than Safari. The person is limited because the locked nature of the device limits them.