You're looking at your analytics reports and everything seems normal. But then you get an Alert via email that says your "cart add" page activity has dropped from 200 per hour to zero. It turns out the page-tagging was broken during upload of a newly developed page that day. You call up the developers and they fix the tagging--and cart-add goes back to normal.
You might have waited days before finding this out via an analytics tool. It was buried deep inside the reports. Dynamic Alert tells you right away.
