This might look like a silly comment, but it really isn't. Let's say FB was nationalised. So now if you want to contact your local government office you do so through Facebook. The library service is accessed through FB. Drivers Licenses and professional certifications are linked to your FB profile as are medical and criminal records.

Government information and services would only be indexed in Google. Amazon would become a branch of the postal service and used to deliver passports and driving licenses. In practice you'd hardly be able to function without using them.

Don't know about other countries, but at least in Lithuania there are laws against such scenarios.

Sure, but in a scenario where the government was so interventionist and controlling that it nationalised a search engine, social engine and retailer how likely is it that such laws would stay on the books?

Nonsense. How can any democratic government force to use Google search, post pics in Facebook or buy from Amazon?

By making the government services only accessible, discoverable, and provisioned by those companies, maybe?