And just a follow up having now done more research. I see the subject was covered in several posts around July/august this year, e.g. Xtrailman's post 2096, also from Dr Watson and Rocketron.
In trawling through the various links I found a Mazda Service Information document R074/14C which included a pretty shocking picture of the camshaft exhaust lobe worn away completely - I would include it but don't know how to!
But it seems there hasn't been any further discussion on this problem, so difficult to judge how big it is. My VIN appears to be in the affected bracket (last 6 digits 161249). So it would appear that Mazda are saying this wear is or was causing the resultant swarf to circulate in the oil system and damage the brake vacuum pump (although I never noticed any brake problem), which the recall was issued to check and if necessary replace - as on my car.
But this doesn't address the root cause of the problem, that of the camshaft wear! Why is the camshaft wearing prematurely (presumably a bad batch in manufacturing), and will it continue to wear, as in the pic I've seen? Why aren't Mazda replacing these bad camshafts? Are they hoping just to get the car beyond the 3 year warranty period - I would have thought those of us who have had the brake vac pump changed could reasonably say, if and when the camshaft failed outside the warranty period, that Mazda knew about the problem (ref their Service Information document), it was therefore on-going and they should repair the car FOC.
A further thought - can one extend the warranty? I might look into this. Hmm.
