Along the lines of the netbook solution, I used my iPad last time I travelled. If you're already definitely taking a laptop, then forget it, but the iPad is a nice light travel computer — and if you already have one, it can actually be a very useful backup tool.
The Camera Connection Kit (works with iPads, but sadly not iPhones) allows you to import photos from most cameras (via USB) or directly from an SD card.
You're very limited by the space on your iPad, and unfortunately you can't write back out to an SD card for a more generic backup or giving you more space (unless you've hacked your iPad/iPhone), so you won't get 200 GB without transferring them OFF the iPad via the internet or a computer. It's essentially letting you duplicate photos on your memory cards before they're backed up by a more serious means.
Judging by your 200GB/year estimate, you'd get a "buffer" of about 3 weeks with a 16GB iPad, 6 weeks with 32GB and 12 weeks with a 64GB — this saves you having to get net access for a few weeks at a time, to send backups home, for example.
You can transfer directly to DropBox, FTP, WebDAV and a few other methods using apps like the DropBox app or GoodReader (supports heaps of protocols), or you might be planning on dumping memory cards to CD at a net cafe or the like once a month (at which point you could wipe the photos off the iPad).
Other advantages are that its a good way of showing photos to people along the way (either by keeping some favourites to show people you meet on the iPad itself, or using it to upload to flickr/etc for people back home). And there's a lot of utility in having a basic computer while travelling of course (e.g. taking a decent stash of books for reading in transit).
Compared to the netbook, it's more expensive for less space (you can probably get a netbook with a 250GB hdd for the same price), so it's really only useful if you're aiming to backup "off-site" anyway, and want something with perhaps a bit more utility than a netbook (a nice screen for photos without taking up much luggage space/weight).
And of course if you hack it, then you could use it to copy photos to SD cards to keep a copy or mail them home. Some people have reportedly got external hard drives working with hacked iPads and the Camera Connection Kit as well, using the USB charger to power the device if it has a double-USB plug adaptor.