https://news.ycombinator.com/item?id=9502169
At least 300 men in the USA share the same name as me. I got my Gmail in 2005 so I got it firstname.lastname@gmail.com and others who got the same name as me enter it into websites all of the time. Most don't even validate the email, and sometimes I have to email the admins to get the account shut down.
I think websites have a resposibility to validate the email and delete the account if it isn't validate in a reasonable amount of time or have a link to delete the account if someone who signed up wasn't you.