Maybe anyone who spent their whole career singing pop qualifies, but the one person with the killer pipes who, to me, has squandered her talent more than anyone is Whitney Houston. And that's totally leaving aside her personal life, documented behavior on the road, etc. A real waste, IMO. and then of course, from another era there's Janis, Jimmi, Jim Morisson, Tim Buckley, Duane Allman, etc. Not really directly on point with respect to putting out crap, but I would argue that these early deaths due to excess robbed all of us of some awesome talent.
Vocalists/Musicians Wasting Their Talent
Since music is now much more about achieving a high publicity profile and making money than making great records, as the ascendancy of artists like Eminem (is that how you spell it?) demonstrates, I wonder if anyone has any opinions about any artists of today or the past, singing in whatever musical genre, who have consistently pursued the almighty dollar instead of maximizing their talent to sing great, memorable songs? I wonder why the recording industry continues to push artists to put out crap when SOME of them are capable of great things? Also, I wonder why artists with great talent and great power in the industry to control their own destiny continue to accept it. Examples and comments are appreciated.