An interesting question. I am writing from a UK point of view, but I would suggest topics might include:
1.Homeopathy- does it work? Is is safe? Should it be regulated?
2.Vaccination - is yearly vaccination necessary? Can 'over vaccination' cause disease?
3.Breeding for shows - Are vets condoning interbreeding and unhealthy dogs? Or are we simply helping animals with problems?
4.Tail docking/ear cropping/declawing - Necessary preventative care or unnecessary mutilation?
I've put 4 as these all seem to crop up regularly in the UK veterinary press.
(I have purposely avoided stating which side of the fence I come down on in all these arguments!)
I hope this helps.
Veterinarian
Qualified from Cambridge university in 2000, I have worked since in small animal practice.