Please help me understand the following:

If I tend to use public streaming API which should show me the flood of all tweets (regardless of the user) why do I need OAuth?
And who is going to be the user granting OAuth permissions in this case? will it be the application user id itself?

Regards,

Our Streaming API system is user-centric and role-based. Historically, the account connecting represents the application – they are one and the same. For the purposes of connecting, the user token that you use should be the owner of the application.