(I'm still computerless and painfully pecking these out on the iPod, but it's getting reduntant announcing it each time.)
Alcohol and I have a funny relationship. I don't drink all that often, or all that much. But when I do drink, two drinks are my absolute limit of rationality. I can hold one drink with dignity, and after two I'll be buzzed but coherent. After three (or sometimes two strong ones, honestly), "coherent" is not a word anyone would use. Particularly not me, because I won't be able to pronounce it.
I'm a cheery drunk, prone to a lot of giggling and not too much trouble-causing, but I am also a ragingly horny drunk. The slender thread of inhibition between me and rampant sexual advances on all my friends and a good number of strangers is dissolved. It's not a matter of me being unable to resist people "taking advantage of me"; I'm out there grabbing asses and taking names. Or occasionally forgetting to take names.
(I also tend to appear somewhat drunker than I am, both because my physical coordination is not much to begin with, and because I invariably start thinking it would be funny to "act drunk.")
Is it ethical to fuck me when I'm horny drunk? I think it is, and not just because I want it. Wait, no. I think it is, because I want it. I may be making different decisions than I would sober (although usually just the ones I wish I would), but I'm making decisions. To me that's consent. In some cases it may be wise to turn me down on a "no, that would be a really bad idea" level, but not on a "no, that would be rape" level. Rape is when a girl says "no" or says nothing or says "yes" under coercion, but I'm pretty sure it's not when a girl says "i'sh wanna fuck you, you shtud."
Because if you insist on waiting until I'm not under the influence, you'll be waiting a long time. I'm under the influence of society, of wanting attention and affection, of some seriously powerful hormones, of how long it's been since the last time, of feeling ugly or pretty or unsure, of a huge potent brew of totally unfair outside factors warping my thinking. If you want me to make a truly unimpeded decision, alcohol is the least of your concerns.
(I also--and this is just me--have a fairly laid-back approach to sexual regrets. If I have consensual, well-remembered sex with someone I really shouldn't have, my emotions don't go much beyond "well, I won't have sex with them again." I've never thought of it as some huge irreversible mistake.)
Drunk sex can be really good, too. I'm all giggly and tee-hee-I'm-so-vulnerable, I'm a bit less oversensitive than usual, and then there's the muscle relaxant effect...