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There is little difference between Site Advisor and WOT. Both are reputation scanners that are subject to those doing the ratings ... like or dislike / safe or unsafe ... it's virtually the same thing on those 2 applications. Any one can post these ratings and this would include owners of malware distributing web sites, malware writers, as well as other malcreants.
If I were one of the above mentioned malcreants, I would be doing ratings on SA & WOT everyday.
It would be best if those 2 applications were discontinued because those who reply on them will be infected sooner rather than later.
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