Think about what it means to be conscious. Consciousness is the integration of all of your sensory input and your memories into a singular subjective experience.
Right now you are sitting in a chair in front of a computer reading English text. To have your conscious experience at this moment you are integrating your knowledge of where you are at this moment, that you are sitting in a chair in front of a computer, your knowledge of what Slashdot is and that the text you are reading is a comment by another user, the concept of what a user is - that it's another person somewhere else in the world, the parts of your brain that recognize text and processes English into thoughts, your memories/knowledge of the concept of consciousness, your awareness that you yourself are conscious, and many other things all at once. All of those things are integrated into your singular conscious experience.
Compare this to something non-conscious, like a reflex. When the doctor hits your knee cap and your leg moves, you aren't integrating the feeling of the object hitting your leg with any memories or objectives. You don't "want" to move your leg, it just happens, unconsciously.
Also think of the way unconscious thoughts "bubble up" into consciousness. Scientists have shown that using brain scans they can predict what decision a person will make before the person even consciously knows. This is because the scientists are taking readings from the part of the brain that is responsible for making that decision before the results of that process get sent back to the part of the brain that kicked off that processes and to the rest of the brain that's responsible for acting upon that decision.
When you really get down to it and analyze it, everything that you would consider a conscious experience necessarily involves the coordination of many distinct parts of your mind. It's no coincidence that the parts of the brain that have been shown to be heavily involved with the subjective experience of consciousness are the the parts that are highly connected to many other parts of the brain.
As far as the strange possibilities for any complex system having consciousness, I fail to see how that should preclude a definition of consciousness involving systems and complexity. Just because the idea of any sufficiently complex system being conscious is bizarre from the conventional understanding of consciousness doesn't mean it's wrong. I think it's entirely plausible that any system with sufficient feedback loops and integration between components could be considered conscious. That's not to say that such a system would be necessarily sentient or deserve rights.
I think what this comes down to is agreeing upon a definition of consciousness and coming up with testable qualities that could be used to confirm consciousness. I think that "A system capable of integrating disparate sensory and past experience into a continuous singular whole" is a good start for a definition of consciousness that doesn't require any kind of non-material entities such as a soul and doesn't necessarily involve subjectivity; simply come up with some tests that could only be completed if the system is capable of such integration. Such a definition would certainly apply to humans and most other animals of higher cognitive abilities.
Some other interesting food for thought: Think about the way companies interact with the outside world and the way they build off past experiences. I wouldn't consider it to be too crazy of a notion that large organizations of people display some level of consciousness.
I am not a neuroscientist, but I have given much thought to what makes me conscious and how other animals can be conscious, albeit on a different level than us, and this is pretty much exactly the conclusion I came to. That consciousness involves the coherent interconnectedness of distinct subsystems. I'm glad to see this topic being discussed, and I'd love to hear other people's opinions of this definition of consciousness and it's implications.