So Coinbase seems to be randomly creating accounts for users using their email address. Is this legitimately Coinbase or a phishing email? The problem is that even if this is legitimate, what gives a company the right to create an account for you without your permission?
It is very likely that you've just been mass-mailed by a spammer/phisher with emails that are designed to look like Coinbase has sent them, but in reality, contain phishing links to a fake Coinbase account in hopes that you'll fall for their scam and send funds to their address and/or reveal your private keys to them.
Either way, Coinbase doesn't randomly register users and send them a email. That would cause a public outrage of breach of privacy, as no one ever consented them to send emails to random addresses.
Your email probably got leaked somehow when you signed up for a site and their email databases got leaked, or they sold your email to other people. It's quite common. Just ignore any email that does not seem normal, and ask the bitcointalk community if you need to.
