I think that being very drunk makes you more vulnerable. If two women were identical in all things physical and mental, in identical situations and one was very drunk and the other was sober, I think the sober woman would fare better. Although I acknowledge that it's possible that if a rapist was also inclined to physical attack or even murder, the very drunk woman may fare better if she was so drunk that she couldn't fight her attacker.
I'm not saying it is the risk. I am saying it is a risk in some situations.
I'm lucky. I live in a very small council estate in a village with a very low crime rate within a local area with very low crime rate. I live a very quiet life, socially. By that I mean that I've never been clubbing (well I stepped into a club for 10 minutes with some work colleagues once), I'm teetotal because I can't stand the taste of any alcoholic drinks. If (rarely) I travel on public transport I am always aware of my surroundings. Even sitting in a local shopping mall's Costa Coffee seating, although I was studying, I was keeping an awareness of movement around me. I always carry a phone. I always tell someone (DH mainly) where I am going, how long I expect to be and when I can be expected back. I always get my car keys out in a lit area before heading for my car. I don't wear heels (ankles turn too easily).
As regards the 'someone you know' bit, I met DH 3 years before we dated, then married him 3 years after that. You can't know someone completely but in the 18 years I have known him he has never shown any tendency towards harming anyone in any way. I never invite a man into my home unless I am with someone, (barring repair men).
I'm not saying I can prevent being raped. Who knows, I could be raped tomorrow. But if I am, I'll know that I did everything I could think of to protect myself from it.