Your comment is precisely why people write the next twitter for facebook instead of curing cancer or solving hunger.

Soylent isn't curing cancer or solving hunger. They're selling meal replacement drinks, which is a large, established market.

Computers were large established market once, but you could not buy one home.

I don't see meal replacement drinks in food stores around, don't think those would be off-the-shelf no-brainer anyway.

It creates a new market.

Could anyone actually (successfully) hold them liable? I'd think it would be their suppliers that would need liability insurance, since they're just repackaging already-approved food items.

Yes, it's basic tort law. They're not just repacking food items, they're combining them in a non-reversible manner. This essentially makes them the manufacturer. Consequently, they will have opened themselves up to liability for every ingredient they use. (But they may be able to go after a supplier for indemnification depending on the circumstances.

Thanks for the clarification! That makes now that I think about it more. I was thinking more along the lines of product manufacturing, which I think is less stringent (honestly I may be wrong there too).

No. Products liability. Everyone in the "chain" can be liable including retailers and manufactureres.

Supplement companies get sued all the time.