It is by definition not spam if you sign up to receive it. Let's not use the wrong words to discuss thing because we get a bug up our butt about a website popup, of all things.

It happens because it works. If bounce rates went up by any statistically significant measure that wasn't more than offset by conversions, sites would stop doing it. There are entire businesses around teaching bloggers how to monetize their blogs, do you think they're not testing the effect this has?

> My policy is to always close the tab when I get an email signup form, and so far I’m sticking to that.

And it's your loss.