Many chocolate products have switched from all cocoa butter to vegetable oil. Cocoa power (and soy lecithin, also subsidized) is way cheaper than cocoa butter.
Sadly many people don't taste any difference (even becoming angered by any attempts to raise awareness) but to me it tastes like cocoa wax. Therefore companies get away with deceptively stating, for instance: "made with 100% cocoa!"
Absolutely no mention of cocoa butter. Yuk!
Another huge food substitute, as mentioned, cheap subsided corn byproducts.
King Corn (excellent documentary)
http://vimeo.com/58736941