Charlie Jane Anders, "Why Dollhouse Really Is Joss Whedon's Greatest Work":
The evil in Dollhouse is harder to deal with than the evil in Buffy because it's our evil. It's our willingness to strip other people of their humanity in order to get what we need from them. It's our eagerness to give up our humanity and conform to other people's expectations, in exchange for some vaguely promised reward. And it's our tendency to put any new piece of technology to whatever uses we can think of, whether they're positive or utterly destructive.
And that last bit, about technology, is the other main reason why Dollhouse is Whedon's most accomplished work, especially if you love science fiction like we do. Unlike Joss' other works, Dollhouse really is about the impact of new technology on society. It asks the most profound question any SF can ask: how would we (as people) change if a new technology came along that allowed us to...? In this case, it's a technology that allows us to turn brains into storage media: We can erase, we can record, we can copy. It's been sneaking up on us, but Dollhouse has slowly been showing how this radically changes the whole conception of what it means to be human. You can put my brain into someone else's body, you can keep my personality alive after I die, and you can keep my body around but dispose of everything that I would consider "me."