I read several times it is a very bad idea and a huge lack of security to use the same proxy for logging into facebook or other sites containing information about real personal details e.g. linkedin and other sites e.g. Stackexchange.
What is the issue with that? E.g. I use an browser plugin and a desktop client Premium-VPN as well, both from the same company. So I am behind two encrypted proxies. And as far as I understand the technology, many other VPN-users are using the same end-node, too. E.g. I log into Facebook, linkedin and stackexchange at the same time with the same two proxies. How can this data linked together and directly point to me, my real location and identity?
Edit: Because someone asked "where I read this": One example was this german youtube video at 9:00 He says, that's stupid to login into facebook via tor, because this definitely identifies you. But why is this stupid? Because you are not the only one using this end-node.
Basically I don't get why am I traceable, when using the same proxy for multiple actions.