Quadrille - 4:26 pm on Dec 3, 2011 (gmt 0)
I don't dispute the ability to use these tools if you are posting low-quality copy on an industrial scale (though I'd question the ROI).
But for most honest webmasters,
1. read the text; if it makes perfect sense, then a quick Google search of a text string will find if there's duplicates.
2. If it doesn't make sense, then someone has almost certainly mangled the text, either a proprietary 'uniquifier' - ALWAYS makes a poor enough job to be seen instantly as the scam that it is. Or they've translated it to a random language, then translated it back; only a dribbling idiot would be taken in.
3. you can't beat a simple glance at the code. That would reveal all known character scams.
And, when paying for product or service; as stated several times above, 'if it looks too good to be true, it probably is'.
If you care about your website; your visitors, your bounce rate, your return rate, your ROI, then you need to set a quality minimum or be beaten by better sites.