In my experience, that's not what happens. My most recent experience with this was when I had gotten about half way through filling out my info for a service, I was sent an email with a price list, I opened it, looked at the email and decided to wait and compare prices with another provider.
Then the emails started.
'Oh hey we noticed you never finished your registration. I assure you our prices are the lowest anywhere'
Had opened the email but never answered it.
Get another email.
'Hey this is so and so, company president or whatever...if you need any more information, about blah blah blah, don't hesitate to send an email'
So I did...I told them I don't appreciate being spammed because I hadn't finished filling out a web form and i'd like them to stop.
Surprisingly, I got an email back from president dude or whatever apologizing and promising to remove me from the email list.
Yeah...right..
A day later...another email. So I blocked them as spam. I still get spam from them.