When is appropriate to use Redirect?

[eluser]MissionMan[/eluser]
When is it correct practice to use Redirect instead of a simple load->view?

The reason I ask is because in the ion_auth demo, there is a comment that states:
"use redirects instead of loading views for compatibility with MY_Controller libraries"

I admit I don't fully understand this statement. If I extend someone else's class library, does that mean that forever after, I use redirect?

Thanks.