Quite apart from the waste, selenium toner is... nasty. I mean the smell. One gets rather used to many of the smells of the darkroom, equating them in one way or another with the artist's struggle and horrible little bedsits on the Boul Mich and so on. Selenium is different. It's the sort of smell that makes platinum/palladium seem like a much better idea.
All of the non-oxygen chalcogens (sulfur, selenium, tellurium, in theory polonium) are known for their unpleasant-smelling organic compounds -- and, as the elements get heavier, the smells only get worse. Sulfur compounds are bad, selenium compounds are awful... there aren't a lot of chemists working with tellurium compounds, but reports are that even trace amounts have a horrific smell.
