The advantage, IMHO, of a databank is that it fits in your pocket and can run off of AA batteries (not sure if the coolwalker was one with a built-in Li or not). Not sure what you have in mind when you mention next-gen touchscreen devices, NikoDoby. If you mean N900 sized devices I'm with you all the way, if you mean 10" keyboardless netbooks I'd rather not carry that around.
I think part of our differing opinions is that I feel no strong desire to show off photos on a portable device. I see these databanks as nothing more than a portable temporary backup.
That said - dual card slots in a camera is a better backup solution, IMHO, while on vacation or otherwise away from your primary backup solution. Using yet another device to (in essence) mirror data from one card to another is just an extra step. sFTPing gigs a day isn't a workable option when the best internet connection you have is your phone. ;) I've never had a CF card fail to show up when posted home, and consider the mail safer than airport security.
For when I'm "in town" I can either backup directly or use friend/family/work's high-speed internet to SSH home and backup. When I'm out of town, be it somewhere exotic like Guam or pedestrian like Manitoba, there is always something I'd rather be doing outside with my time than looking at photos or backing them up.