> It's illegal to destroy evidence of a crime but it's not illegal to avoid creating evidence in the first place...
One can see how regular folks might consider the practice of automatically destroying chat and email messages after one to three months destruction of material which could be evidence.
"Never erase anything" seems to work fine for highly-regulated businesses like banks. And while long-term storage of electronic communications isn't free of charge, it's not at all in the same ballpark as storing decades of paper memos and other paper internal office communications.
Also: The widespread directive to "magically" turn documents into privileged communication with lawyers makes Google's bad intent very, very clear.