Which had more impact on the net?

I vote for #3, if you are considering a purely technological / routing Point Of View, which is the point of this mailing list. Affecting the backbones hurts everyone, everywhere, trying to do anything on the 'Net. The other are two localized (either in type or location) to matter overall.

NIMDA did not affect e-mail, chat, IM, et cetera (pretty much), and did not even affect most web servers enough to matter to end users. News web sites being down did not affect anything other than the news web sites being down. And the destruction of a couple COs within a few city blocks (*and* a few city blocks :-{ ) is not - from a purely technological / routing standpoint - that big a deal.

OTOH, #1 has a much more lasting impact. From increased traffic on web sites for years to come if this drags out, to the affect on "disaster planning", to the impact many of us who help run the Internet feel (I know I do), September 11th will have a much more profound impact on the 'Net than fiber cuts, especially in the long term

But then, even if not one fiber was cut, not one website saw increased traffic, and not one colo was damaged on September 11th, it would still have a more of an impact than the other two in a lot of ways which are hard to measure at the command line of a cisco or Juniper.