I would not be surprised in the future to see a lot of countries attempt to ban foreign social networks. Basically, with Facebook, Twitter, and LinkedIn, the US government has defacto access to a treasure trove of who knows who, who influences who, and want skills everyone has. This information would be very expensive to collect by intelligence services, but with these US companies, is just handed on a platter.
Basically, if you are a geopolitical rival of the US, you would have to be a fool to allow your people to use these American services.
Well there's another school of thought: if you want to be a significant world power (prerequisite to being geopolitical rival to USA) you have to let your citizens read whatever they want, vote however they want, and join what the fuck ever social network they want.
The article doesn't describe how the ban is technically enforced. I'm not aware of a great Russian firewall so I speculate it's either self-enforced (LinkedIn agreed to reject users who enter Russia as their country), or enforced by ISPs.
The first is unlikely, the second is easily bypassed.
Yes. There are many smaller firewalls of Russia. Every ISP by the law has to maintain the system on their expenses and obligated to periodically download state ban list. Various ISP use various technique from simple ACL to DPI in various combinations. Here is current black list https://reestr.rublacklist.net/
Need to say that gov agencies periodically check ISPs if they indeed ban sites and re-offenders are fined.
Mostly ISP sysadmins reports their list downloaded from roskomnadzor + reports from users about blocked sites, since some bans a communicated by direct orders and are not shown in roskomnadzor lists, there are few and mostly temporary but they exist.
Not sure who it helps. Low-earning Russians weren't really using it. High-earning ones that need to use it, e.g. Russian investors, will just be finding ways to still use it - VPN, travel to Estonia etc.
Basically, if you are a geopolitical rival of the US, you would have to be a fool to allow your people to use these American services.