@rob, I applaud your vision for Soylent and continue to follow its development with interest.
My point in urging comparison of Soylent to certain other engineered foods with R&D-intensive nutritional design histories isn't to discourage further development, but rather to suggest that past efforts be learned from. We'd do well to focus more on differences in actual compositions and health effects and be less dismissive about differences in intended uses and/or marketing.
What's worth mentioning in comparison to Soylent? I'd agree that Plumpy'nut®—a ready-to-use therapeutic food (RUTF) for treatment of malnutrition in famine situations—is indeed instructive. Moreso than considerations about how long one might survive on just cow's milk, human breast milk, the exclusive source of nutrition for newborns for the first 6 months of life (or longer), spurs important questions about changing nutritional needs over a human lifetime.
Or consider the extreme requisites of food for prolonged spaceflight and NASA's Advanced Food Technology Project, with its eyes toward a mission to Mars. Ask why their visible efforts appear nothing like dehydrated Soylent. Is NASA on the wrong track or is their different approach all due to the additional constraints of low weight, high shelf-life and psychological appeal?
Six years ago, my father's surgery for throat cancer resulted in losing his ability to speak and needing to intake his food through a PEG tube (his epiglottis was damaged by radiation and he'd repeatedly contracted pneumonia from food particles entering his trachea). He was on Jevity® 1.5 for a brief time. Later, he had a surgery to separate his esophagus and trachea completely, such that he now breathes through a stoma and has regained his ability to intake liquified food orally. Today, he continues to rely on carefully considered homemade formulas and meals that my mother blends for him.
It's because I take the potential of Soylent seriously that I'd be concerned if those enthusiastic about it seem to overstate its novelty, or fail to see that a different vision for a product does not necessarily make a product different.