There's an economist, Arthur De Vany, who says that steroids are a red herring. I am not qualified to judge his argument, but it's interesting.
I guess that the standard argument is that steroids make mediocre hitters hit the few balls they hit a lot farther than they would, and they let mediocre pitchers throw faster. So they let mediocre players overperform.
De Vany argues that most people who do steroids don't get better at baseball, that the things that count most (accuracy, timing) steroids don't affect, and that while they can make you stronger (in conjunction with an amount of training that would have made you stronger anyway, to a lesser degree--there is something to say about steroids making people simply *want* to work out more), that the kind of strength they build is slow-twitch muscle that would not help you hit a ball any farther.
I don't think the data stands up to his argument. Something has to account for the massive increase in homers. I agree that Bonds is one of the greatest ever.