Disaster awaits. Of course it does. The news media are running out of stories. The demise of the internet is the news of the day. Today is 9/9/99.
How will this interesting date affect most people? Most people probably won't realise anything has happened until they write the North American short date format on something. "Oh, nine nine ninety-nine. Neat."
Of course, having said that, some networks and servers will have problems. Hoping to hide within the expected terror of the 9/9/99 viruses that never were, many malicious people will try to cause damage to people's computers and networks.
I have a feeling, however, that much like any other tribulation, we'll bounce back somehow. I mean, cyber-terrorism? Who fears terrorism? Doesn't that take place in countries where the women uulate and beat their own heads when they're upset?
The next interesting four of a kind date, incidentally, will occur on the first of January, 2011. Will there be more threats and fears regarding problems then as well? Count on it.
Of course, the world is going to end at midnight (but in which time zone?) on 1 January 2000, so any problems after that will be moot, anyway.