Oakland has made a ton of mistakes over the years. The idea that they don't is asinine.
How about trading Carlos Gonzales for Matt Holliday? Or basically giving away Nick Swisher because they thought they had their 1B of the future in Daric Barton, even though talent evaluators thought he wasn't going to hit enough for the position? How about letting Josh Willingham go only to have to trade for an OF who's certainly not going to hit as much in Chris Young even though they have other CF options?
And this is my point about the risk, by the way. When teams don't spend big money, the mistakes don't appear as big as A-Rod's 10-year contract or the Crawford signing, but teams make a lot of mistakes year-in, year-out.