Is it time to start calling out bad cyclists?

There are really 2 things happening here. Firstly these people are pointing out of hazards and signalling what they are about to do, and that is unquestionably a good thing, although a few glances behind would be a nice addition. The second thing, and the one that I think is irritating some of us, is that they are ostentatiously using what they think is the secret language of the serious cyclist to demonstrate their superior promuter credentials. After all you've spent 6 months salary on some carbon, slithered into a skin suit and slathered your danglies with Official Sky Team(tm) chamois cream so pointing left with your right hand and yelling "car up" every time you see a cab coming the other way is just the logical next step.

That'd be "car down" though.