To me it doesn't happen often, but when it does, it's a huge annoyance. Basically it stops you dead in your tracks of whatever you were doing and sends you on a frantic hunt for what tab is causing it. The usefulness of a feature that solves problem is (n times p happens * annoyance of p) - at least that's how I prioritize features. So yeah - I've searched several times a year for a plugin that does this, for at least 5 years back.