I have to thank Leafy Green Sewage - New York Times for getting me to ponder whether someone other than spinach farmers are at fault for the unedible spinach:

California’s spinach industry is now the financial
victim of an outbreak it probably did not cause, and meanwhile,
thousands of acres of other produce are still downstream from these
lakes of E. coli-ridden cattle manure. So give the spinach growers a
break, and direct your attention to the people in our agricultural
community who just might be able to solve this deadly problem: the beef
and dairy farmers.

Another article (A Stopgap for the Spinach Lover) answers a question that I've been wondering about -- can't we just cook our spinach?:

The Food and Drug Administration has advised
people not to eat any fresh spinach at all, not even cooked, although
sufficient cooking (160 degrees for 15 seconds) kills E. coli O157:H7,
the bacterium that has sickened scores of people around the country,
including at least 18 who are critically ill, and killed at least one.
The agency is concerned that even if the spinach is cooked, bacteria
may have been left behind on a countertop or a knife, which could then
contaminate another food being served raw.

At any rate, I worry about the future of salads of uncooked vegetables
in general. What's to stop other vegetables from being tainted in the
same way?