How important is it to consider the Grid for my back-up data center & DR Plan?

It has been several years since the August 2003 Blackout, but I can't help thinking that we are all being lulled to sleep on the next major grid issue. There are only 3 main power grids in the US so if I have my primary Data Center on the Eastern Interconnect then should my DR requirement be to locate my back-up site in TX on the ERCOT Grid or in the west on the WSCC Grid. Or is there any benefit to locating on a different NERC region in which case there are 10 regions in the US. Can that benefit equivalent to being on a separate grid? I would doubt it since the 2003 Blackout crossed multiple NERC regions in the Eastern Grid.

http://www.eere.energy.gov/de/us_power_grids.html

Should I not be concerned with this & just choose a site or build a site with a higher level of redundant & back-up power? Is it more important to have the DR site in a location easily accessible for our technical experts than it is to have it on a different grid? Remember 911 grounded flights so if we had another event of that magnitude it would take days for my technical experts to get to our DR site if they could at all. Of course we can introduce many tools for full remote control & power control where access to our physical environment becomes less important so should I make it best practice to get that DR site on a separate grid? If I put locating my DR site into my key design criteria where should it fall on my priority list?