Dude it's 2012...gigabytes haven't been precious for over a decade.

Neither has bandwidth. :-)

Only 3 GBP / MB when roaming. Remotely viewing a movie with a high-res encoding might only cost approximately the same as a car.

Why don't you just buy a local pre-paid SIM? Though I guess most of the time I'm travelling I'm on vacation, so don't need to be reachable on the usual number. That might be an issue if you're on a delegation.

That's fine in theory, but you have to find a reasonable deal, find a shop to purchase it in, familiarize yourself with how to charge it up, and all in the time you spend in that country. I've found it burns at least half a day - usually not worth it. Most of my leisure travelling is motorbike touring, and I may spend each night in a different country, or cross borders several times a day (mountains with interesting roads are frequently on borders).

If my travel was simpler, sure, it's somewhat workable, and I do have e.g. a German SIM. But it's usually better to just rely on hotel wifi, cached maps on phones, offline GPS on bikes, etc.

When travelling it often is. Mobile data rates are still prohibitively high in most places and wifi services have low caps.

Only if you are at 'home'. If I where to use 3G on my phone when traveling in the US, I'd pay $17/MB! Even a 3 hour drive from my house (a trip a regularly make) will put me in a new country and I'm paying $7 for the first 50MB and then $3/pr additional MB. That makes watching movies kind of expensive.

While offline?

Not so much. If you're going to need to view video away from data service or WiFi then, yeah, you have no choice but local storage.