When you try to dial a number in area code 212 at Yahoo!, it’s really easy to end up trying to call the cops.
A number like “9 1 212…” is easily misdialed as “911…” by missing the first 2. Of course, they intercept “911” calls even though they are not fully qualified. (You’d have to dial 9911 to get the real 911, although I think they intercept that here, too.)
So it goes like this:
Jeremy dials 9 1 212 but misses the first two, notices, and hangs up to try again.
Phone rings.
Mission Control: Mission Control, 911 was dialed from this phone.
Jeremy: Ooops, I was trying to call 9 1 212 …
They must get that a few times a day…
Jeremy Cole 
I’ve done it at least twice now.
A lot of companies change the “dial-external” prefix to something other than 9 for precisely this reason (especially in the case of phone systems that recognize “911” and don’t intercept but immediately send it through to the local E911 service).
“7” is a popular alternative prefix, but it really depends on the internal exensions.
I’ve done that twice already. Good to know they are right on top of it.