I'm fine with the idea of meal replacements, but:
1) I think they already exist. They just aren't marketed to trendy 20-somethings. (This is what Soylent does well and why, I assume, they're getting investment. The actual product can be completely reformulated until it comes reasonably close to being a good meal replacement: It's the brand that's become valuable.)
2) The Soylent team sounded like such snake-oil salesmen out of the gate that they simply don't have much credibility, as far as I'm concerned. With all of the made-up benefits they touted at the start, now they have to dig themselves out a deep pit of bullshit to actually demonstrate the value of their product.
It's important that we don't treat this kind of food product like a toy. Which is why it's important to be critical of unsupported claims. (And critical of supported claims, as well.) Especially those made by young people with no particular background in the field they're purporting to be experts in. Food is not a toy. It's not Tumblr. It's not Zynga. It's something we require to survive.