Comcast blocking some Internet traffic

MSNBC is reporting that Comcast blocks some Internet traffic. The article speaks for itself, but essentially reports that Comcast has taken steps to block some peer-to-peer uploads/downloads … by inserting into the "communication" between the two machines:

But with "peer-to-peer" technology, users exchange files with each other, and one person's upload is another's download. That means Comcast's blocking of certain uploads has repercussions in the global network of file sharers.

Comcast's technology kicks in, though not consistently, when one BitTorrent user attempts to share a complete file with another user.

Each PC gets a message invisible to the user that looks like it comes from the other computer, telling it to stop communicating. But neither message originated from the other computer — it comes from Comcast. If it were a telephone conversation, it would be like the operator breaking into the conversation, telling each talker in the voice of the other: "Sorry, I have to hang up. Good bye."

Now, I don't do file sharing, but I wonder whether this is really about file sharing of illegal downloads, or just bandwidth usage. If it's about bandwidth usage, what happens to those of us in the Web industry who upload files to webservers? I mean, I don't do it all day long, but if you build websites, you've got to do it.