I like your sense of humor and find your theory interesting, Boycey.
Certainly, Winky was willing to protect the Crouch's and their secrets . . . she was very loyal to her masters, even though her blowing the whistle on them, as Dobby tried to on the Malfoys, might have spared a great deal of pain for all.
I don't think, on their own, house-elves would commit evil acts . . . could they be used by evil, 'death-eater' masters to do bad things? It's entirely possible. There are lots of house-elves in Hogwarts, and yes, DD probably would not have them there if he didn't feel he could trust them, but then, he *isn't* an evil master. He has no reason nor would he ever ask them to do things or cover up things of a evil nature.
That in mind, unlike the dementors who would most likely gladly serve Voldemort, as he could give them great *fulfillment*, the house-elves aren't inherently evil. But I do believe they *could* be manipulated by those masters of house-elves that are.
The house-elves, as evidenced by Dobby and Winky, are privvy to all sorts of information that, if known in advance, could head off a good number of bad things happening. However, the very nature of house-elves is that they are loyal, and the punishment they could face for being unloyal could be quite brutal. I wonder if Dobby isn't going to *pay* for his indiscretions later down the road . . .
