Disclaimer: The following are just personal opinions based on my firm desire to fly until I'm old and grey - not rules, regs, or guidelines. It's late and after reading what I realize it's strongly stated. No offense meant, no need to get defensive, and not a 'my way is the only way' lecture.
jrh said:
Rediculously dangerous? Because you might run into another aircraft? The airspace is Class G for a reason...because there is nothing out there. I think the big sky theory would apply.
Also, by the last portion of your post, it sounds like you won't go IFR off-airway. Never GPS direct anywhere? As for obstacle clearance...if you're up at 13,000 or 14,000, you'd have to be in some very high terrain to violate the 2000 foot clearance rule.
Honestly, I'm playing a bit of devil's advocate here...but I don't know if I'd call it "rediculously dangerous" either. To me it sounds like the kind of thing that is acceptable if you have a reason for it, otherwise you ought to avoid it. Probably shouldn't do it just because you can.
Rediculously dangerous (RD). Yup, in many cases. Nothing out there in G?

Antenna farms, hills, mountains, water towers, other airplanes, and on and on. G isn't G because there's nothing out there. It's G because radar coverage is spotty. Why does G stop at 14500 MSL? Because the highest mountain in the lower 48 is 14493. Above that, there's no problem with radar shadow. But there is certainly stuff out there!
To do it the way it's been suggested here, it would be RD. First, the big sky theory sure as heck won't keep you safe forever. There may be another guy out there and you'd have no way to know until he was in your cockpit. Thats RD.
There was also the suggestion that you could go 'as low as you want' and do 'whatever you want in G'. Good luck. Unless you have GPS, you may not have nav coverage. No nav coverage in IMC is RD.
Obstacle and terrain clearance is also huge. Unless you're above the grid MORA/OROCA, you've got no assurances. Flying below that, especially in the G under a 1200 or 700 foot E shelf? Again, RD.
Not to mention that there are no approaches (that I know of) existing entirely in uncontrolled airspace. Following the suggested "Go lower until you break out" method mentioned earlier? RD.
Off-route and direct? All the time with a clearance in controlled airspace so I know there's nobody else lurking in the clouds waiting to tag me. Also above the grid altitudes for obstacle clearance and at altitudes that allow me to pick up a VOR if the GPS goes South. And in an area where I can grab an approach if I need to get down for any reason. However, enroute, at altitude, and when you know you can get to VFR or onto a clearance before descending below a safe altitude is one place that the risks might be acceptable.
Alaska? It sounds like it's SOP with known factors. I'm guessing they know the terrain, have some type of procedure to guarantee obstacle clearance, have an 'out' if they don't get on top, and make the departures away from the approach course. I'm also assuming it's used when you can see the sun through a thin layer of local fog and know you'll be out of it momentarily. That would mitigate risk to an acceptable level in some cases, for some pilots.
The situations and conditions where the risk is low enough to justify not doing it the conventional way are very few, very far between. Earlier, I was saying that, according to regs, it's possible. But I never endorsed it as a way to go for the average Joe in a situation where it's possible to do it another way. When it's the only way, when risks are known, accounted for, and reduced, it might be reasonable. But those situations are so few and far between that most of us will never be in one. I've done a lot of unusual flying in places where there's a lot of G to abnormally high altitudes and I have yet to find a situation where I personally saw need to use this particular trick.