PACs are healthy for democracy. But corporations and unions have a different legal standing, and federal law has prohibited them from playing a direct role in federal elections for many decades. That prohibition has been undermined by soft money and sham issue advocacy. Internet-based disclosure of contributions will be a commonplace very soon, but it doesn't deal with the question of who and what must be disclosed. Students and senior citizens have the time to volunteer on campaigns, but a time-pressed business owner doesn't.
Private contributions provide an important form of political participation.
With no limits on the sources or size of contributions, business executives are subject to not-so subtle pressure from party and public officials. Extortion is more a problem than bribery, in my view. Today I saw an article by him about campaign finance reform in the Seattle Post-Intelligencer, the morning newspaper. But my impression is that he is so confident of the wisdom and righteousness of his position on campaign finance that he has little patience with conflicting views. For example, he's never taken any of my arguments or evidence seriously.