You're one judge's pen-stroke away from having personal property seized and then it's just a matter of how real your machine's physical security measures are.
Quite true. If you, personally, are a target of the NSA, you are totally fucked. We know that they will make up evidence if they cannot find some.
However, we put locks on our doors even though most of them can be picked very easily. Why?
Security best practice is "defense in depth". You defend at each level to make it more expensive for an attacker. The goal is to make attacks against your stuff more expensive.
If you make the government have to dispatch someone physically, there is a vast amount more friction. There was an inspector from Scotland Yard who once commented that "If your drives are encrypted such that it takes us more than 40 hours of work, your drives are not going to convict you. We will spend our time on gathering other evidence." Physically seizing a server is annoying paperwork.
So, the goal is to prevent them from being able to dragnet low-level offenses for cheap. If you're a murder suspect and they have good reason to come after you, then they're coming after you irrespective of the cost.
Google is likely to have more legal resources to fend off unjust requests to access to your data.
We all know Google is doing it, though.
What, precisely, do we "know" Google/Microsoft/FUDCo is doing? Certainly not willingly collaborating with every quasi-legal search and seizure presented to them.
But you (or perhaps upthread) are implying that Google willingly hands over data to government authorities.
The evidence would point to the contrary: Google (and Microsoft I might add) are complying with the law, but are not simply rolling over and handing out whatever is asked of them.
Their ability to fight back against unwarranted requests is probably much better than someone running their own mail server in their basement.