Those are probably at the top of my website annoyances list. "Want to get more like this in your inbox?" -- I don't even know what "this" is, you barely let me read the first paragraph before asking!

I'm sure the conversion rate of those things is being tracked, but somehow I can't believe that would even lead to a single newsletter signup. Who on Earth feels like they're not receiving enough e-mails and subscribe to the first mass mailing that asks? Maybe some people whose browsers auto-fill their e-mail address and they click the wrong button to close the pop-over?