I just want to attach an anecdote here and explain why I prefer confirmation emails.
One day, somewhere in the last couple months, I checked my email box and saw a message from some craft site. It was informing me that my paid subscription was activated and that I was entitled to X, Y, and Z services. I ignored it. I received another related email the next day. I ignored that, too. When I received a third with another advertisement, I realized this was legitimate and that someone had accidentally used my email address! My inclination was to find someone in control of the site and let them know the mistake so that the original person could see their offers and track their subscription. I headed to the website and noticed the login form on the first page.
Curiosity struck me. Was this one of those sites that people make fun of online with bad security? I clicked the link saying I forgot my password. They asked not for my username but for my email address. So I entered that. Next thing I know, my Inbox has an email from the craft site with the registered user's plaintext password!
Uh oh. Is this for real? What if I was a malicious user? I had to see how bad this situation really was. I logged into the user's account. I was able to find their home address and phone number, but thankfully (dear Lord, thankfully), the website made no mention of credit card numbers. I did not look to see if I could order more service; at that point and in my shock over the situation, I felt I was deep into some weird grey area and was way past my welcome. I logged out, found an online contact form, and explained the situation as well as how they could improve their system to avoid harm to their users.
The security mistakes in this situation were compounded.
(1) Email alerts went to the wrong person. If you verify the email, the right people get the messages. If you do not verify the email, the wrong person can mark your site as spam or take advantage of the situation.
(2) The site stored plaintext passwords. This was a craft site... By the name of the victim and other factors, I realized that this was some old lady who has faith in the trustworthiness of the Internet and probably, like most typical people, uses the same password for multiple sites. And this site happily handed it over to a stranger. That, my friends, is scary.
People make honest mistakes. If the email address is important for account management, send a verification email. And give the user an opportunity to fix the problem in the event that that verification fails in some way.