I actually found this popup both useful and unobtrusive.
In this particular case, as my mouse cursor rolled over a link in the story to Amazon, up popped a little graph showing the share price movement.
When I moved the mouse away, the popup gently faded away.
Normally, I dislike popups that appear when you move your mouse over links as they tend to suddenly emerge in an unexpected and unwelcome manner. The worst are the in-your-face ones that generate a little screenshot of a website and those on sites where it seems every other word is a link that produces a popup ad.
This one on FT.com, though, shows how to do it well.