I suggest that Armstrong does not quite belong on this list though, or at least not at the top. On the negatives: He cheated his ass off in a sport that is almost more about cheating than riding bikes. Lance lied about cheating, and attacked those who said he was cheating by accusing them of being liars.
On the plus side, Armstrong took a marginal niche sport and brought it fame. No one would give even half a **** about a tour de france winner cheating if not for his accomplishments. And before Armstrong, no one would have thought you could earn $100 million riding a bike. Armstrong also started a massively successful cancer charity that is probably second to only the whole pink ribbon / tit tumor charity. Also, the whole becoming an absurdly champion after losing a goddamn nut. Sure he cheated, but plenty of his peers with more testicles were cheating just as much.
I figure he more or less gets a pass in terms of harm done vs good accomplished. Whereas Barry bonds cheated his ass off, denied it, and despite making nearly twice as much money as Armstrong, did pretty much nothing of benefit to humanity.