How tough it is depends on how you're engineering your geo-redundancy. I've been doing it since 1998 and a simple active-passive solution is not as hard as some would believe but it does cost money. Active-Active is much more challenging and multi-master is obviously the ideal and the most difficult to engineer with geo-network latency. I haven't seen one solution that couldn't be staged to at least provide active-passive DR capability for a pretty reasonable price. You can even do it in EC2, RackSpace Cloud or Joyent if your feeling "cloudy".