I first noticed several projects involving money exchange posted on Freelancer.com and opened tickets having noticed this to be strange. This indicated a strong message - There is a major security issue that a set of people are exploiting. While I reported it in vain and felt sad for those who were going to fall for this one but didn't realize I would be the one to be scammed very soon.
I had several projects (all web development) I was invited to and paid for which were suddenly reversed without any intimation. The reason provided was that the payments were made using stolen credit cards which they somehow expected me to be aware of!
When I planned to move out of it is when I realized a bigger problem. I had grown as a freelancer and earned a reputation that warranted paying the fees that I did. I had built a level of trust that does not come with portfolios of hundreds of projects or testimonials from people on your website. Because, well, there is no authenticity.
But by growing within freelancer, I had neglected forming my offline network. I did have a good client base I had got from there but not enough to sustain without new ones as the work was never regular. I had missed a very important step : creating a brand for myself outside of a third-party platform. Ensuring a good client base outside and ensuring that you use these platforms to only supplement you.
After raising the issue of multiple reversals, I was contacted by senior staff and compensated with a subscription and promised that I could always check with support team to find if a user was genuine. Shockingly, I was no longer allowed to withdraw funds and the support team do not respond to any questions regarding the same!