Anne Midgette has a provocative article in the Sunday NY Times Arts & Leisure section called "The End of the Great Big American Voice." There is an accompanying audio presentation on the Web, with Sylvia McNair contrasted with Dolora Zajick in interesting ways.
My only significant objection: why hold up Andrea Bocelli as an example of what's wrong with vocal training, and especially American vocal training??
He's an Italian pop singer whose original technique is oriented explicitly to the microphone. Now, maybe that is the point, since part of Midgette's thesis is that smaller, tamer voices record better than bigger, more unruly voices. (I agree with her that it's a problem in the business and an issue in how singers are trained.)
Still - Bocelli is attempting to sing opera today largely as a marketing and sales ploy, not because it's his natural arena or because he is the slightest bit suitable for opera. He was not quite laughed off the stage when he tried live opera on for size. He's not the best example for Midgette's article or the audio piece, I feel. Pick one of the half-voiced operatic tenors floating around out there instead, even if he's less famous than Bocelli.