What are the cons of classified information belonging to the U.S. government being leaked?

If we talked about something one time, say, bombing Disneyland with chemical weapons, and then we find out the Government knows about it, we can figure out how they found out. Did we talk on skype, or email, or cell phone? We can figure out what they are monitoring, and find another way to communicate, which the Feds may not be monitoring.
Mickey gets gassed because we got tipped to the Feds procedure.

When a government has just a few secrets, it is of utmost concern that those few secrets must be protected from leaking.

When the government is classifying 16 million documents per year, and intelligent citizens of the Republic are saying they need to, because we are scared and they are protecting us somehow, then we no longer live in a functional Democracy.

It there are 16 million things a year going on that the people can’t know about, then we are too ignorant to vote, and shouldn’t be allowed to. Of course thinking about it a minute, a wise person realizes that no government needs 16 million secrets, and most of these things should absolutely be in the public domain. Then it becomes obvious that the leakers are heroes of a sort, and trying to save democracy.

All successful deviants speak in code, expecting their communications to be compromised.

So the next time you see “Grandma wants some ice cream”…
...it really means “The shit is about to go down”

It is no bother to them being monitored. It is only a bother to law abiding citizens, and the data overload NSA has foisted upon themselves with our money which should be spent on our failing education system instead.

Leaking is justified when laws are being broken, like war crimes that happened in Iraq. Manning had a duty to leak this.