At different points in time American ISPs have blocked Skype, Vonage and other VOIP systems, electronic wallet transactions (I think such as Googlewallet), and the most famous being Netflix. These all took place from mid 2000s to right before the net neutrality regs were put in place.
The argument against neutrality is that it is stifling ISP innovation and leading to reduced network investment. This is made dispite at least one ISP publicly admitting that net neutrality hasn't affected their network investment.