The reason I love these sites is the flipside of the reason most writers hate them. They're very lucrative for me.
See, I know my strengths as a writer, and two of them are that I'm very fast and that I don't agonize. So while I agree in theory that it's an insult to offer a professional $8 or even $17 for a 500 word article, my hourly rate cranking out these articles often exceeds my standard freelancing rate of $50/hour.
A friend recently suggested that I was somehow cheating the system; he believed that the agencies that used these sites intended to pay writers minimum wage or less. Because they didn't know how fast I was, he felt that I was sort of tricking them into paying me more. But I don't think those clients care how much I'm making an hour. I think they want a decent-quality article for a few bucks, and that if I can provide that they don't care whether it took me two hours or two minutes to produce.
I know there will be writers who think I should refrain from making $40-60/hour on these sites because they're not lucrative for most writers, and I'm not even going to address that here. We can talk about it in the comments or another post if you wish, but I've written quite a bit already about writing for cheap/free and why my views differ from conventional wisdom in the industry.
What I'm getting at here is that what constitutes a "good gig" for one writer isn't necessarily what pays off for another, and that rather than thinking in terms of a black and white generally accepted hierarchy, anyone who wants to make a living as a writer should figure out what his or her strengths are and then find the market or the job or the niche that makes those skills most profitable.
For me, content production sites are easy work that isn't especially interesting or demanding, but offers flexibility and quick payment. I wouldn't want to do that kind of writing all day every day, but a few hours a week provides a nice little supplement with very little investment.
What's your secret strength?