A newsletter is useless to you, but a lot of people like them. I agree that popups aren't the way to push it, though. A simple newsletter link in the header of the site is more than good enough. I don't care how good the "conversion" rate is, I don't like harassing people who are just visiting my site for the first time.
Same. Mostly because of tracking. According to what's been getting published in various internet marketing sites, one of the primary reasons why newsletters have become so popular for sites to do isn't about the newsletter -- it's about getting the email address (that's also a reason why more and more sites are requiring an account even when it doesn't make technical sense). That's a decent identifier that allows you to be tracked across sites.
Then there are the rare cases where you do subscribe, but every link in the email is a tracking link. Because they need to know when and from where you clicked on that link. SMH.