The term "unskilled", which is commonly used to reference these types of workers, is an economic term used to distinguished types of workers by characteristics like low education levels, minimum wages, and limited economic value. The skill you are talking about is called quality assurance and customer service, which as you rightfully point out is "skilled". Finding unskilled laborers who also possess those talents are incredibly difficult to not only find but also train.
> Those who claim flaws in matching business model are to blame are making non-quantitative assumptions
Here's a really easy quantitative assumption. Go on Craigslist and get quotes for similar services direct from the workers themselves, then compare it against Homejoy. That's called a gross margin and it's incredibly low. That's an inherent flaw.