The public is largely unaware of just how much control third party governments give law enforcement. They can manipulate your search results to hide information from you or promote certain things they want to be presented to someone they are looking into.
If the historical basis of this access is being able to read the list of library books you check out, now it has expanded to controlling which books are recommended to you and they have the ability to control the content of the media you receive.
A common dismissal of this issue is that nothing can be accessed without court orders or a subpoena. It's important to remember that this is only really true if they intend to directly use the information obtained from you in a court proceeding. Often times it is about information gathering on a target that is not meant to be used in court. Even then, they have endless ways of using a form of parallel construction to hide the source of the information. This also extends to data brokers, which have to work with the Government to continue operating. The same is true for app developers who want their apps to be listed on app stores. Or device manufactures that want the ability to sell their products and pass FCC certifications...
In more serious cases, it extends to the concept of your identity itself. Law enforcement often will not hold itself accountable for violating the laws or your rights. Identity theft tied to online actions against you is not out of the question for them either. When it is taken this far, good luck reporting it and having it resolved.
The stuff they can do with the backdoors in YouTube, the advertising system, cloud document storage (LE can view your live work in cloud storage like Google Docs, etc... Imagine working on a lawsuit against someone watching you formulate your legal arguments)... It just goes on and on...
End rant