I work in a data center in New Orleans, and so I am fairly familiar with this topic. Of course they're vulnerable. If you live in a region like this you better have a well thought coop/dr plan. We have a hot Site an actually migrate production services there several times before hurricane season and testing services there is part of our development/test process before things go into production. Outside of that, our building was designed to withstand a category 5 storm but the biggest problem is power. We are good for 72 hours on fuel for our generator, but if a Katrina size storm hit again refueling could become problematic. Also, there are personnel issue (evacuation orders, etc). If im at a small data center (relative to amazon/fb/etc) I would have to guess they are already all over this.