What is a "Scam" Site (2)?

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Oops, I posted this in the blogger.com forum, meant to post it here. My interest is specifically in PTC sites, but I am sure the question applies to most online money making sites. I see the word "scam" thrown around a lot and I am not always sure what people mean by it. At the end of the day, it seems that is just mean, if you do the work or pay money, the site won't pay you. What's strange to me is that the word "scam" to me suggests an intention by the owner of the site to defraud you. But what about sites are run by inexperienced, incompetent admins, are they scams? How about someone trying out a payment scheme that ends up not working, etc... Anyhow, what do y'all think it takes for a site to earn the name "scam"?