Whistleblowers often receive criticism, and Snowden is very similar to a whistleblower. Yossarian's comments have some weight, because it is natural to realize that whistleblowers like Snowden have both pros and cons to the information they leak. On one hand, it was good to show that the NSA may have extended boundaries, but there is some bad too.
Snowden was a fictional character in the Catch-22 book. There is no possible way that there is a connection between Edward Snowden and the Snowden that is portrayed in the book. It is an interesting coincidence, but it is not the same thing. Edward Snowden is a character of a modern era.
Edward Snowden, the NSA whistleblower, is not the same as Yossarian's tail gunner from "Catch-22." The character dies after the plane in which he flies takes anti-aircraft fire. Yossarian is a major character who forces his crew to go on mission after mission, thus creating the popular term "Catch-22." Snowden the whistleblower stood up to his bosses. Snowden the character died a needless death. The new Snowden is not the old in that the former NSA employer is alive and well. He also isn't fictional.
Edward Snowden is now a polarizing figure, but he's not the Snowden of yesteryear foretold by Yossarian. That Snowden would have a much larger impact upon society than the leaker that revealed NSA security programs. However, Edward Snowden will be remembered as a big figure in history as far as the 21st century is concerned.
Edward Snowden is not a special person that any one told of would come in the future. Rather he is a concerned individual who did what he thought needed to be done. He thought the government had crossed a line and that the people of the US had a right to know what was going oin.
No, Edward Snowden is not the Snowden of yesteryear that Yossarian was referring to, because Yossarian was only referencing a metaphor. Yossarian was not talking about anyone specifically. There are parallels, because Snowden's actions and Yossarian's work briefly touch on the same subjects, but you cannot say that Yossarian was prophetic in his references to Snowden.
Edward Snowden is an American who worked for the NSA and was a whistle blower to controversial surveillance collection. Yossarian's Snowden was a chatacter from Catch-22 who died in his arms during a battle. Yossarian and Snowden were good friends and his death changed him for the rest of the book.