Simply put, the grape is a dud, producing chirpy little wines wholly devoid of complexity and depth, the very qualities that make wine interesting and worth savoring.
What's with the poo-pooing of whole grape varieties in the USA? First it was Chardonnay that was "out", now Merlot seems to be in the firing line (seen "Sideways"?), and now Sauvignon Blanc? It should be about the taste of the wine, not whether the grape being used is currently in favour or not. (What next? Grape tabloids? "Did you see how fat Pinot Gris is getting? She's so over the hill!")
A little harsh, methinks. Sure, most Sauvignon Blancs are fresh, crisp and refreshing and do not have the "complexity" of heavier white wines (which are often oaked to hell and gone). But sometimes you want that - it's like having a nice refreshing salad instead of pate de foie gras. I think packing good flavour into a light, crisp white wine is as much an art as making a lush, opulent red. (But then I'm a yobbo that actually likes some heavily oaked Chardonnays every now and then)
I tend to drink mostly reds, but have had some good Sauv Blanc in the past, most recently a 2004 Southern Wright (from South Africa, of course). With the sunshine and warmer weather finally making themselves felt in Seattle, I'll no doubt be buying a drinking more white wine than red.