I can't believe this isn't an ability already. It's a quick fix that would save hours of manual entry time. This looks like it had been requested 3-4 years ago with no answers from staff! Please add all contact fields into the "mass update" menu.
You can select multiple contacts in list view, but somehow you can't mass update them to all be associated with an account? And you can't pick a multi-select box to mass update either? The field names already exist in the contact details. Why can't I click them?
This would not require any extra infrastructure--all that's needed is to add the field name in the "mass update" drop down menu. Such a quick addition.
I would even be happy if you could click the "+ New" in related lists and add contacts, but this doesn't happen--you can only create a brand new contact, you can't add one that already exists, but you can do this with products and other items!
There are going to be numerous times when someone needs to add more than 1 contact at a time to an account -- trade shows and conferences both come to mind.