While I was not born and can not personally comment on the Jimmy Hoffa disappearance, I have noticed a pattern when it comes to the government and people that disagree or reveal things about them that they do not like. The people usually end up missing or dead. I would never speak out against the government for that fact alone, so I do believe it's possible that the government had a hand in the disappearance of Jimmy Hoffa.
In today's media, there are always conspiracy theories about every major new story. Jimmy Hoffa's disappearance was an important news event, and, naturally, there are all kinds of conspiracy theories surrounding it. However, there is not substantive evidence to support the theory that the United States government was behind his disappearance.
A mob hit on Jimmy Hoffa created one of the greatest mysteries of the 20th Century in 1975. The United States government should have done more at the time to locate Hoffa's body. However, the crime family that kidnapped him was too quick and too powerful. Only the Genovese crime family knows where Hoffa's body is at this point. They can't be prosecuted because investigators need a body as evidence.
There were many people in the US who stood to benefit from the death of Jimmy Hoffa, a very powerful union leader, and the US government was probably lower on the list than most. Hoffa and his union had extensive mafia connections that he had previously angered, so they are a better candidate.
Jimmy Hoffa's death wasn't a government conspiracy, it was a mob hit in the middle of the afternoon in Michigan. The FBI couldn't find his body, although they had suspects who allegedly had alibis. The two suspects were part of the mob, but they disposed of Hoffa's body so quickly the government couldn't find it. No one may know what happened to Jimmy Hoffa.