Rousseau would probably say that a business's interests are inherently selfish and not in line with the general will of the populous. Businesses, in my mind, are not members of a republican government. An argument as to why they are will frankly never make any sense.
Additional edit: There is a huge amount of evidence that can be seen already about how businesses wreak havoc on political systems. The United States is a perfect example over and over again. Whether is it government intervention in the forming of labor unions, military intervention around the world and in south america (especially the early 20th century), corporate sponsorship of congressional members, etc - we can already see that this is a thick cloud over our representative government. Noam Chomsky has written extensively about this. Our senators and representatives are continually caught up in this via lobbying and etc. When you let businesses into the process as much as we have you will have problems - but if you allow them further access beyong what they currently have then that would be absolute insanity.
Additional edit: There is a huge amount of evidence that can be seen already about how businesses wreak havoc on political systems. The United States is a perfect example over and over again. Whether is it government intervention in the forming of labor unions, military intervention around the world and in south america (especially the early 20th century), corporate sponsorship of congressional members, etc - we can already see that this is a thick cloud over our representative government. Noam Chomsky has written extensively about this. Our senators and representatives are continually caught up in this via lobbying and etc. When you let businesses into the process as much as we have you will have problems - but if you allow them further access beyong what they currently have then that would be absolute insanity.