I recently made a new site for SEO education. Should I use popunders? Do They really increase profit, or just annoy visitors?
Well... they do both. They are really annoying, but they do increase profit. It is a personal choice, but I would refrain from popunders as it will kill most returning visitors. If your site is a "one time see all" site, then you will want to get the most bang for your buck and you can use popunders.
I usually tend to stray away from popunders because it annoys your 'loyal' user base, who you need =D
Annoying. That's the first thing I close when the page is loading. I'd personally steer away from them.
Anything that pops is definitely a nono. It maybe was a succesfull tactic a few years ago, but nowadays alot of users use a popup blocker which will kill them anyway and might annoy them so they stay away.