Thanks for pointing that out; your comment led me to read the Ars article. I was then compelled to go Nature and read the article and its accompanying News and Views. Interestingly, the News and Views opens with the same profound point (that the unit of sleep appears to be single neurons) that you referred to in your post. My point is only to note that the Nature folks address in the first line what it took the Ars reporter an entire article to get at.
Quoted for reference:
"An accompanying perspective makes a separate suggestion: the fundamental unit of sleep may be a single cell. When an animal is sleep deprived, individual cells are more likely to take themselves offline. By chance, that will eventually start producing the clusters that produce local sleep events. Over time, the frequency of local events goes up, and the neurons begin to coordinate their activity, ultimately producing the large-scale rhythms seen in sleep."
Nature News and Views: http://www.nature.com/nature/journal/v472/n7344/full/472427a...
Nature News: http://www.nature.com/news/2011/110427/full/news.2011.259.ht...
Nature Article: http://www.nature.com/nature/journal/v472/n7344/full/nature1...