Is it illegal for governments to start their own social network? I imagine it could be a lot of fun. Have a section for the block, the city, the region, and one

Is it illegal for governments to start their own social network? I imagine it could be a lot of fun. Have a section for the block, the city, the region, and one for the country. Create contact lists, market places, business and personal pages for each? Use the same laws we already have for public space? Am I missing something? Are toll roads the future?