reply to swhx7
Re: WOW IANAL, but copyright violation is always spoken with respect to distribution. Thus, end users can modify copyrighted works without legal repercussions because they are end users. However, anyone who is retransmitting the copyrighted webpage would be violating copyright if they modify it. And if they're using it to make a money, it's a criminal violation.
Injecting advertisements is definitely illegal for this reason. Injecting status messages is a gray area. Any revenue made from the injection of status messages is likely to be indirect. Hence, while Google can sue for copyright violation, it would be in a civil court, and only for lost revenue, possibly for defamation, defacement, what have you.
Also, there are agreements between providers that prohibit discrimination of data. So if data goes through a certain provider from Google to your ISP before getting to your computer, there's likely a violation of that agreement.
It's not a net neutrality issue per se, but there are still legal issues to consider.