From my own experience and followup I can confirm that they did shut the addresses down that I reported. When they did not, I reported them again.
It's still far from ideal, and I hear what you're saying, but that should not stop you from continuing to report them. They do eventually take action.
I'm speaking specifically about GMail here. Yahoo and Hotmail are both still woefully inadequate. I would still like to add that Hotmail has recently undergone some kind of shake-up. Before this month I had to report to four (4) distinct email addresses:firstname.lastname@example.org@email@example.com@msn.com
And I would immediately get four auto-response messages, then a day or two later, a very lengthy response.
Now I get three distinct responses in that second step, and they aren't always the same or from the same people. They appear to be taking much more action on these reports. I still have to report it to all four addresses because I get conflicting responses from each about which is the correct address.