Do the employers on these freelance outsourcing sites really pay their workers

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or are they just scam sites? I ask this question because I visited one of these sites and I click on the bidder's profile page and to my surprise there were no bidders from U.S, nor the U.K., or Australia. What I want to know is why there are not many Americans, Brits, or Australians people bidding for these jobs with the world economy like it is? It make me wonder if a lot of these workers get paid for the work once they have submitted the work to their employers. I found the site to have loads of article writing jobs of all pay rates. Even the writing jobs which are asking for Americans and Brits workers don't have any Americans nor Brits bidding for those jobs. hey! folks what gives? ...