In general there are a lot of good business ideas that die pretty fast once everyone and his mother start using it.
I remember once people started adsense arbitrage, then parking arbitrage, then some arbitrage with craigslist was happening. People earned 10th of K USD per month with that, some built a house and whatever but these methods died all pretty fast once they became known as well working methods and everyone told his friends about it.
so true on this one
most who say they freelancing will never tell (my main freelancing is local in my country i do 2-3 off in whole year)
yes there are sites for that but sometimes there so cheap project that i dont wont to bid on them and sometimes to many bidders are in project with good quality that you spend time for nothing
still here is sig excellent and trade the right coin for profit (current is BTC to DOLLAR and other way around)
It is like they dont want anyone else doing this kind of jobs that offered to them specially when it is easy. They dont the mass online workers to be there also and put it at risk of stopping it. Just like spammers in a signature campaign. When that happened the company is the one who will take all the consequences. Quality assurance is the other reason for keeping it secret.