Here is the deal. Sure major companies do steal things at times. But they also know that it is more beneficial to buy the product or rights from that person, depending on what it is. Why cut off the access to the creativity/ability a person has buy stealing a product? That individual could have many more useful ideas, products, or inventions. It is situational though, not a blanket statement.
The biggest issue with the USPTO is that they will follow their outdated protocols to deny or approve patents, trademarks, copyrights, ect. As long as you fall in the perimeter of the process and pay the money they want, then you get the rights to your idea. Protecting that idea is up to you. And in some cases the court will side with the individual that the idea originated with and not who owns the rights. But do you have the money to fight?
Advice: Don't let someone stealing your idea stop you from being productive or releasing a product.