Read just this particular thread! I posted links to other people's troubles over the fake check (money order, etc.) scam. It's fake, fake, fake, it's a scam. NO ONE PAYS IN ADVANCE FOR WORK NOT COMPLETED. PERIOD.
How this works is you sign up with a company on a secure site, you get a user name and password, you get guidelines and a report form on the website, you go TO THE WEBSITE to report, and after your report has been reviewed and accepted, you get paid a few weeks later. Usually payment is $10-$30 per assignment.