I too would love to know, if that actually works. Does anyone have any data on this? As an engineer, I would push back HEAVILY if an employer asked me to do something like that.
We ran an A/B test at a former employer a few years ago that showed that the popover was somewhere in the range of 1.5x to 2x as effective at getting signups than anywhere else in the page (sidebar, header, footer). I left the company shortly afterwards, but I'd assume the trend doesn't hold and may even reduce engagement long-term. We also cookied visitors to avoid annoying our users.
