Have to throw my 2p in. Apologies in advance for the rant.
There may be some drivers for whom this technique is appropriate, and there are probably some roads on which it is appropriate but I'd contend that it's a dangerous technique to suggest for most drivers - myself included. It requires a level of concentration ahead of and behind the car and knowledge of the road - hidden entrances as previously mentioned, hidden dips and the like - that yer average driver probably doesn't have most of the time. It probably also requires regular practice, which is something that police advanced drivers get but 19 year old Zack who is driving a mile down the road to his best mate's house twice a week probably doesn't.
It is far, far safer to stick to your own lane all the time, and if you find you are flinging the car around a bit, for heaven's sake, slow down, but do it early and don't stand on the brake just before (or worse, on) a bend. The difference between 40mph in a straight line and 30mph to "go around" is probably less than ten yards and five seconds, including a bit of engine braking on the approach and mild acceleration on the exit.
There are several roads around here where people regularly cut across to the wrong side of the road, because it makes for an easier drive, but where it is positively dangerous to do so. One of these places is literally a hundred yards from my front door. The road makes a fairly tight "S" and people think they can see around the bend, but they can't - there's a small part for both directions which can quite easily hide most of a car, and (to coin a phrase) I've lost count of the number of times I've left the house or been returning to the house, come around this bend and found someone making a frantic swerve to their left because they suddenly realise they're heading straight for an accident. And they're usually doing 5 or 10mph above the 30mph limit anyway, on a bend where even I (and I enjoy going around corners quickly) find 30mph is pushing it a bit.
We're also at the entrance to a set of lanes which are a bit of a rat-run for delivery drivers and people who set "shortest path" in their sat-navs. There are a few places where it is good to be able to drive straight through a "wiggly bit" and there are plenty of occasions where you might position yourself "unconventionally" in the road in order to avoid a pothole that the council has left to grow wider and deeper for the last nine months, but in general, even where the lane is barely wide enough for two cars to pass, it pays to "tickle the hedge" - that is to drive with a wing mirror close enough to the hedge that it brushes occasional stray bits of bramble (but watch out for broken branches, especially after storms).
It also pays to practice reversing using only your mirrors while not driving into a ditch or up the bank.
There is one particular bend where you can tell the regulars apart from the occasionals - it's a sharp bend to the right, uphill, with the road narrowing quite severely after the bend, having a ditch on one side and an 8ft tall block wall on the other. There happens to be an entrance to a forestry car park just on the bend, so regulars will "dip into" this entrance so that they can see around the bend and have time to stop safely and leave enough room for anything coming down to pass. Occasionals won't and then sometimes find themselves having to reverse back around this bend. I've also had people try to overtake me on the bend because they think I'm pulling over, even though I haven't signalled.
Driving is only partly about the mechanics of it. A huge part is awareness of your surroundings, and I'm afraid (as someone who drives around 24,000 miles a year) I meet people every day who obviously aren't taking notice of what is going on around them. The simpler the rule, the better.
Oh, and if any one of you is visiting Cardiff soon, be aware that the council is in the middle of making pretty much the whole of north Cardiff a 20mph zone, even where it is utterly inappropriate, that there are confusing signposts up (one way you see a 20, 500 yards later there's a 30, but 50 yards after that there's a 20 on a lamp post, while coming the other way there's no 30 zone at all) and that people get so frustrated if you actually dare to stick to the speed limit that they will overtake on double-whites, across junctions, on crossing zig-zags, by ducking into (for example) left-turn-only lanes when they want to go straight ahead, and even occasionally by using bus lanes to get past you.
I used to enjoy driving.