Most companies, banks, hospitals, gov agencies, etc. really don't have any security measures in place for stopping bogus NEW registrations for existing offline customers. All they do is ask for some background info that just about any family member might know or could find out fairly easily. Then they send an email verification to whatever address they were given.
Watch what you leave lying about when your sketchy uncle comes for a visit.
My wife and I take advantae of this all the timee. She will sign me up for stuff I have no interest in to get discounts or free stuff. I'll use her name in more women oriented businesses and to keep my identity out of the process. In that sense she's my firewall.
I manage a family member's finances. I have full legal power of attorney. When I took over, there were no online accounts of any kind for this person but, in this age, all of the billing offices actively push "going paperless." I don't bank online nor advocate that anyone else do it. But when it comes to doing a change of address for -say- medical records then it takes miles of red tape and a couple of bureaucrats' attention to get it done. OR I can just go online and fake it.
But the thought also occurred to me that it would be pretty easy for a rogue family member to abuse this, hence this thread.