Network-wide sign in created accounts for me on all sites even though I had no accounts there beforehand
A few day ago, @aCVn proposed that there should be a network-wide sign in to avoid signing in into each sub-site individually. I upvoted the proposal because I like the idea.
As of yesterday (19.06.2020) it's been implemented and rolled out.
Now there is something that wasn't mentioned in the initial proposal or maybe it's hidden between the lines and I didn't catch it.
To try out the new feature, I logged out and logged back in and tried out every site. Suddenly, I have registered accounts on every site even though I specifically didn't sign up for them. For example, I didn't sign up for Electrical Engineering as I neither have any knowledge of this topic nor do I have any questions related to electronics. Of course this could change but then I would have registered on this site.
Is this the intended behaviour?
If it is, I do want to raise a few concerns. If in the future, some site will skyrocket because it evolves around a highly dynamic topic, is very popular or Codidact just happens to be the #1 site for this topic, we will see a surge of new users asking questions and answering them. Now all of the sudden, we also have a lot users on all other sites even though the new users primarily signed up for the popular site.
Of course, there is the possibility that some users like to participate on other sites right from the start and will do so but I think that most users will just stay on their respective start site and sometime later they might enjoy to participate elsewhere or not.
My problem with that is that we now have large user bases everywhere even though participation hasn't changed significantly. New users coming here might see this and think: "Wow, so many users, someone will answer my question very quickly!" In the end, the hoped-for answer takes much more time as the users who participate answer it at their normal rate. Beside this point, some users might ask themselves: "Why do we have so many users and nobody's participating? Just registering and then doing nothing?"
A solution would be to only have a network-wide sign in for the sites one has actually registered beforehand. An alternative is to display a hint that one always registers for the whole network and not just this specific site as this hint is missing on the sign up page right now.
I think that this should be made apparent as it also corners privacy issues. Normally, I expect that when I register an account on any website that I only have an account on this specific website. If this isn't the case, I expect that's explained to me. (For example, Google displays a hint which tells you that you register one account for all their services.)