So 'much' mistakes

Saw this sentence in a wire-service dispatch about Ivan:

His storm rations included as many chips, pretzels and bottled water as he could buy.

Of course, there's a little problem there. You can't buy "as many" bottled water. You can buy as many bottles of water and you can buy as much bottled water, but it's not a good idea to mix the two.

Why do we seem to have so much trouble getting series right?