Some people find them annoying. I've seen people bombard their site and can tell there's no strategy behind them.
Has anyone split tested these successfully? Can't just run these on the entire site. Any strategies would be greatly appreciated. Or some case studies would be make it so much cooler.
I'm planning to test the testimonial notification vs the recent purchase notification on the shopping cart, along with testing the time delays.
What would be cool to test in the future would be to trigger these based on time on page, video viewing time and scrolling length. If, they work at all...