I have spoken before about the need for freelancers to be careful when applying for jobs. This is especially true when a HR person states they must contact you through Google Hangouts. This blogger actually documented the process these scams take.
Still, even the most knowledgeable and wary freelancer can succumb to a scam or even lose money because an employer does not pay him or her. As of yet, I have not been "scammed" but I have lost money from non-payment. This is why I am a strong advocate of methods of pre-payment like Guru's SafePay. The employer is required to verify their bank and deposit funds with Guru before you begin working. When the job is finished, you get your money from Guru. That said: If you are hiring a freelancer and you need a job done ASAP, make sure your accounts are set up and verified so you can immediately transfer funds into the escrow.
It took me two times before I made SafePay a mandatory part of my contract. In the first case, I had written a book with an employer and they hired me to write a second one. I had no problems getting payment for the first book, so I did not require an upfront deposit for the second one. In addition, I had done my research, and this was a valid company. I turned in the product, and the person who hired me said they would send it off to review and get back with me for any changes I needed to make (just like the first book). Two weeks passed, and I had heard nothing. However, some employers are like that. I waited a full month (which was the "up to" amount of time I had been told, even though it had only taken two weeks the first time). By the time I contacted the company, I discovered (1) The person who hired me was no longer with them (2) No one knew anything about the manuscript I had submitted to her and (3) that meant I wasn't getting paid. This showed me that even a legitimate company may not pay you for your work, and you really don't have any recourse since the person who signed your contract was no longer with them.
The second one was a Christian publishing company. Yes, I know, my grandma would be like "any business can SAY they are Christian." I had been dealing with them off and on over small projects for a couple months. They were based in the Caribbean and had sent me $25 projects. Then, I was told I needed to write an entire book based off a person's live sermons in one week. This was a huge (expensive) project, but they were willing to pay. Of course, I had to start immediately to complete it. Then, I was supposed to contact the minister. The minister was not a nice guy. I would explain how the book needed to be done and what I had done with the chapter, and he wanted me to make all these changes--which took a lot of time. I was writing the book for him, but he wasn't my boss. The guy who hired me then told me to stop talking with him and just finish the book. He believed the minister was trying to deliberately hold things up. So, I did. I finished, and, I never got paid. The guy who hired me kept telling me that he was having trouble transferring the money to Guru. Sigh. In my mind, it is easier if I just believe the minister never paid them for the work and that is why I never got my check. But, that was the end. Everything must go through SafePay now, no matter how many times I have worked with an employer.
I know UpWork offers a similar payment protection escrow. That is why they are the only other online freelancing website that I recommend. Working with a payment protection is the only way to prevent scams, too. When you tell a scammer that you are not going to give them your bank account, but they can send the check or direct deposit to Guru, you will get resistance. You might cringe at the paying Guru or UpWork a commission on everything you earn, but if they save you from being scammed, it is worth every penny.