Since this concept has been making its rounds on the various boards and blogs I read, it feels appropriate to weigh in, in detail, on this subject.
Affirmative consent is the idea that avoiding a "no" in a sexual encounter is insufficient for true consent. That only a verbalized "yes" to each and every act performed is sufficient.
I'm actually quite fond of the idea.
The biggest stumbling block I run into when quietly contemplating a better legal situation than the current age of consent, or arguing for its abolishment in open forum, is the fundamental fact that our current system of consent for adults is fundamentally broken. We let adults abuse and manipulate one another in ways that should rightly horrify any human being of good conscience. Thus the idea of exposing children to those culturally and legally sanctioned abuses rightly causes us all to recoil from the idea.
I don't like recoiling from ideas. When I get that impulse, I choose to dig deeper. To find out WHY that reaction strikes me. Because if I recoil, I can't learn specifically what about the situation is so inimical to me, and I can't examine if those distasteful parts can be excised.
The way I figure it, if it isn't acceptable to do inflict something on a five year old child, it isn't acceptable to inflict it on an adult either. If you think we need an age of consent to protect children from predatory adults who would lie their way into bed with them, there is no valid justification for treating those same predators as harmless or even admirable just because they're doing the exact same thing to other adults.
Now, that isn't to say there aren't serious flaws with the concept of affirmative consent. Firstly, like all aspects of sexual consent in this culture, it's gendered, in that males need to get consent, and females need to give it, never the other way around. Not a problem specific to the concept itself, but a problem inherent in our culture and one that rightly needs to be called out whenever the subject of changing the standards of consent come up.
Second is that how far it needs to be taken is never sufficiently defined, nor will its proponents ever submit to limiting cases, always shreaking about their "better safe than sorry" nonsense. Under reasonable standards, this practice could force better communication between sexual partners, make everyone take accountability for their own agency in deciding to participate, and reducing the tragedies that currently result from our current standards of "implied consent". If stretched beyond reasonable boundaries, however, it becomes a standard no one can ever live up to, and thus redefines every sexual interaction as rape, with all the gendered and ageist asymetries that go along with rape accusations in our culture.
Some claim that this standard infantalizes women, because it denies their ability to speak up when something is bothering them about a sexual encounter, and instead relies on the man to ask for confirmation. Aside from the obvious sexism in the idea that only a man would need to be held to this standard (not that it isn't an objective fact of our culture that this would be the case), I actually agree that it's infantalizing. That's why I like it so much.
Maybe if we can get the level of discourse and behavior of the general population to a place where a child would have no difficulty navigating it, why would we need the age of consent or anything to replace it?