Well, I quibble about the "multiplier effect" (which I admit I haven't seriously studied at all), since it's my understanding that it ignores the costs of taking out all that debt (but since I guess this happens in a period when no one wants to borrow anyway ... well, as I said, I haven't seriously studied it :-).
However the "can't survive contact with real humans" is spot on. One thing you left out as I understand it is that you're supposed to pay back the money you borrowed after the economy recovers. This of course never happens.
True, some countries do decide to seriously pay back debt, I understand Canada did a lot not too long ago, and we paid back a lot of our WWII debt, but those are not the same thing.
And countries that run their operating budgets on ever increasing debt inevitably renege on it one way or another (getting conquered was not uncommon in times past), with I suspect the recent technology based boom (say the post-WWII one) being a special case of the game being able to last a lot longer than normal. (I.e. that's our (the hackers) fault :-).
My fundamental quibble is that for the multiplier to kick in, the central spending authority must not only invest in certain things (the part our real-world stimulus failed), but it must invest successfully in projects that also bring value to society. A Keynesian stimulus isn't just paying 10 men to dig holes and 10 men to fill them in, it's paying 20 men to build an important road or something, usually infrastructure, of other importance that will bring wealth to a society. To get the multiplier you must both put money into the otherwise-jammed society and obtain something of value for the money. Skip the second part and you just lost a full 1x factor off your multiplier.
This is where I say that even Keynes could tell you this stimulus would fail. For instance, there is a local road that even as I type is being "repaired" with stimulus money. But it didn't need repair. Where a $1 of stimulus here is supposed to produce, say, $1.20 in "stimulative value", now we're only getting the $0.20 in value. That's not stimulus. That's actively worse than letting the funds sit there, actively worse than the worse case that Keynes fears; now you're destroying capital. Not only does that not help avert the worst case, you actively bring it closer! And this is the "good" part of the stimulus that is actually infrastructure, too.
Granted, not every project wastes %100 of the capital, but an analysis of the actual stimulus shows the vast bulk of it does; most of it essentially puts useless and wealth-destroying institutions on life support so they can continue destroying wealth. You don't have to guess what the resulting consequences are, you just have to look around.
As an Austrian I believe (with some reason) that a central government is not capable of deciding which projects are actually valuable, any more than a central authority can set prices of any other kind. Moreover, in a relatively efficient economy (it doesn't have to be perfectly efficient), the big infrastructure wins would already have been built, leaving only the dregs behind, things that weren't already built because the economy has decided they aren't of value.
So I think right at the heart of Keynesian economic policy is an enormous "... and magic happens here...", right where the stimulating government entity determines how to allocate the stimulation. Which, if you note, rather precisely and correct predicts how the stimulus fails in the real world, which is that it was very inefficiently applied regardless of whose standards you apply, Keynes or otherwise. A Keynesian must believe that this was a poor application of the stimulus concept, but that hypothetically a government usually gets it right, despite my inability to come up with examples of said; an Austrian like me gets to continue believing that governments are foundationally and structurally incapable of efficient allocation of resources.
That said, my family and I have used CCC infrastructure out in the west in times past. Good investment? Don't know, we were vacationing.
A relevant example this many decades in the future? I seriously doubt it, as you note in your comment on dregs. Which is I gather a lot of what happened in Japan in the last two decades: they've now got some really super-duper infrastructure all over for a steadily aging and decreasing population (peaked in 2006 and is now accelerating downwards: http://en.wikipedia.org/wiki/Demographics_of_Japan#Populatio...).
However the "can't survive contact with real humans" is spot on. One thing you left out as I understand it is that you're supposed to pay back the money you borrowed after the economy recovers. This of course never happens.
True, some countries do decide to seriously pay back debt, I understand Canada did a lot not too long ago, and we paid back a lot of our WWII debt, but those are not the same thing.
And countries that run their operating budgets on ever increasing debt inevitably renege on it one way or another (getting conquered was not uncommon in times past), with I suspect the recent technology based boom (say the post-WWII one) being a special case of the game being able to last a lot longer than normal. (I.e. that's our (the hackers) fault :-).