I would heartily encourage you to dig into the story more deeply. I think you would find it very interesting.
The method you suggest, of keeping documents in a safe at work, is in fact, exactly what Wen Ho Lee did. He kept documents in secure places at his work. Unfortunately for him, the government did not think his places were secure enough, and they also (like Drake) decided to retroactively classify a bunch of material he had and declare he was committing Espionage. Your method, IMHO, does not guarantee against prosecution. The Espionage Act section he is charged under refers to 'retaining' information - keeping it in your safe at work is 'retention', as Wen Ho Lee discovered.
Drake knew he would probably be fired. He describes this in the Mayer article and elsewhere. He felt that he needed to stand up for the law and for the taxpayers, and that this was more important than his career. He took many precautions but he also knew some of the risks. He just didn't imagine that the Executive branch would spend millions of dollars chasing down the Tamm / NY Times leak on warrantless surveillance, and somehow wind up at his door. Drake and his associates were targeted because they worked on an Inspector General complaint in 2002. Drake later gave unclassified non-sensitive information to a reporter. This is why he was targeted, not because he violated any law.
Mr Drake and Bradley Manning are, in fact, charged with almost precisely the same piece of legal code. Subparagraph (e) of section 793 of Title 18 of the US Code. Drake is charged with 'retention' of information while Manning is charged with 'delivering' information 'related to the national defense'. The funny thing about this particular subparagraph is that it was created in 1950 as part of the McCarran Internal Security Act, which was shoved through during the Red Scare era. President Truman vetoed it but Congress overruled him.
Manning has 34 counts against him; only a few of them are for allegedly violating the Espionage Act. One of those is for leaking the Collateral Murder video.
If he is convicted, that will become precedent - leaking gun camera footage to the media will be placed up there with what Aldrich Ames and Robert Hanssen did. If Drake is convicted, there will be more precedent. Discussing unclassified information with a reporter could get your house raided, your documents 'retroactively classified', and get you 35 years in prison.
Imagine what effect this will have on the freedom of press.
1. He did not mishandle classified information. There are 5 counts that each refer to a single document.
One of the documents is clearly marked UNCLASSIFIED - the government claims he should have known it was classified
Several other documents were classified -after he was indicted-. It's called "retroactive classification", and it has been used before in bogus Espionage cases, especially Wen Ho Lee (who later won a million dollar+ lawsuit against the government).
On top of all this, the portion of the Espionage Act that he is charged with doesn't even use the word 'classified', it only talks about 'national defense' information. What is that? Good question - there is no hard, fast definition. The jury has to decide at trial.
So why does the government keep harping on the word 'classified'? good question.