For the record, at least in my field Arxiv is where the action happens and journals are an afterthought. I don't put placeholders for contact details in my preprints because 1) the adresses likely won't change between drafts and 2) lots of readers are going to be reading that version so I want them to have access to the real info.

Of course most of that is moot for professional scientists because you likely know (or at least be able to find out about) the authors already. For example some papers have old non-working email addresses for the authors who have since moved institution. It's not a problem, since I'll just look them up by name if necessary and usetheir current email.