A packet is a block of data (called a payload) with address and administrative information attached to allow a network of nodes to deliver the data to the destination. A packet is analogous to a letter sent through the mail with the address written on the outside. A packet preferencing is a restraint that one obtains through the internet. Internet is supposedly a system of liberty, where one can surf and browse through websites of their interest. This kind of emancipations is destroyed by preferencing. This could really exasperate the internet user. For example if the user wants to visit a certain website but if the preferencing does not allow to view the content of the website that is important to him. This could result in to that person's lack of knowledge.
This kind of preferencing might directly affect some of the day-to-day users as they may not be able surf or browse the website they used to just because the preferencing doesn't consider it to be good or useful.
Right now people are surfing the website without any prohibition by their own will and they are not used to accepting the rejection that are made by the preferencing. So suppose if the preferenicng is put into action than the user might loose complete interest form the internet. Many of the users might even complain for loosing their freedom over the internet.
I think that the purpose of the packet preferencing is to allow things that are important and block the content that is not important. Suppose if some person wants to view the website with foul contents than packet preferencing might block the website from opening. Suppose if there is a chain letter form destination A to destination B then that letter might get regarded as a useless thing...