If you are specifically targeted in an investigation [...]
The purpose of services like DDG is to reduce the amount of casually collected, personally-identifiable private data you might be strewing about - data that might potentially be recovered and might potentially be used against you or used in ways that you don't like.
If you are specifically targeted by an investigation, a law-enforcement agency like the FBI, armed with probable cause and warrants can tap your phone, search your house, track your location, log your keystrokes, etc, etc. DDG can't help you there, you'd also be vulnerable even when using a service provider which really doesn't have access to your data, like tarsnap. DDG is not going to magically protect you from targeted (and perfectly legal, civilian, non-NSA-related) surveillance if you happen to have the bad luck of being a subject of such an investigation. It's a silly standard to hold any service provider to.
The purpose of services like DDG is to reduce the amount of casually collected, personally-identifiable private data you might be strewing about - data that might potentially be recovered and might potentially be used against you or used in ways that you don't like.
If you are specifically targeted by an investigation, a law-enforcement agency like the FBI, armed with probable cause and warrants can tap your phone, search your house, track your location, log your keystrokes, etc, etc. DDG can't help you there, you'd also be vulnerable even when using a service provider which really doesn't have access to your data, like tarsnap. DDG is not going to magically protect you from targeted (and perfectly legal, civilian, non-NSA-related) surveillance if you happen to have the bad luck of being a subject of such an investigation. It's a silly standard to hold any service provider to.