I would likely be millions of dollars richer if I happened to record a two minute conversation with my former boss's boss, who was an ecclesiastical leader at a church that I eventually left. He told me point blank that the reason I was fired was because I wasn't faithful enough and was no longer worthy of my (completely unrelated) employment. On the books, however, they made it out to be a performance issue. I had plenty of witnesses available to me that could have proven that it wasn't a performance issue, but in an at-will company, that doesn't get me anything at all.
I don't go around recording random conversations, and corporations have a lot of ways to cover their tracks. When that is your reality and the burden of proof is on you, you don't do anything. You get fucked and you learn from it.