I voted that it should only be done with approval. The reason is that some companies depend on that bandwidth. For example, in 1998 I "rented" an office in San Francisco from a company called MedWeb which provided online X-Ray, MRI, and other image transfers between doctors. The office was part of a project I was working on for Intel on their iGames.org web site for the Cyber Cafe's that they were supporting.
Before I moved into that office I started up the Quake2League.com website and was hosting the Deathmatch Database for Gamespy and running Quake 2 tournaments. That got shut down by pacbell because I started getting too many visitors to my personal web site...they claimed it was abuse.
After getting into the office I continued to work on my tourney software and expanded it to provide real-time scoring and TFC server features such as auto-kicking engineers who dismantled their teammates sentries. I soon had two 24-player TFC servers running which had an average of 1,000 players joining each day.
Then one day the owner of MedWeb noticed that his network usage meters were getting maxed out but he wasn't seeing the billing statements from his customers. He noticed that my network card LED's were blinking very fast and pulled the power cord out of the wall. Needless to say I had to notify everyone that the servers were going down. If I had talked with him about my project he probably would have allowed me to run it in the evenings or worked with me to increase the bandwidth.