In economics, “borrowing against the future” means investing money into the economy, and hoping that the GDP will rise by a percentage higher than your debt did. Are there any notable examples of when some country passed a large spending bill to increase the economy, which then failed and put them into debt?
Taken very broadly, I would say that a large chunk of the Western industrialized world had, before covid, and even before the 2008 crisis - if you look at a long enough time period - already been doing this to some extent, as many were often running deficits and had generally rising debt relative to their GDP.
Poster boys for this would be Italy, Japan, Greece. Japan most notably tried to "spend itself back to health" by massive road public works for example.
I am not claiming that deficit spending, in Keynesian terms, is bad and useless. Only that it should be cyclical in nature, not running semi-permanent deficits, leading to rising debt loads.
The term "Stagflation" refers to any situation where slow economic growth is accompanied by high inflation - the worst case scenario for state borrowers: their income isn't growing, and the cost of floating their debt is rising rapidly (most national debt has a portion which is maturing every year and must be refinanced).
This was the case in many nations during the 1960s and 1970s, and various monetary policies taken by nations wound up being counterproductive.
The consequences here were not because of 'betting against the future' per se, but if the rest of your monetary policy isn't aligned properly, you can sabotage such efforts quite easily:
This recession was so exceptionally deep precisely because of the monetary policies of the preceding 15 years, which had unanchored inflation expectations and squandered the Fed's credibility. Because inflation and inflation expectations remained stubbornly high when the Fed tightened, the impact of rising interest rates was felt primarily on output and employment rather than on prices, which continued to rise.
At the municipal level in the U.S. the entire practice known as Tax Increment Financing (TIF) is prone to a whole slew of problems, not the least of which is the failure of property values to rise in response to the TIF'd development project. This can cause cascading financial issues, as it did in Kansas City, and these can contribute to the absurdly high rate of municipal bankruptcy in the United States.
Designing TIF contracts is an incredibly difficult balancing act for professional, technically-expert public finance specialists; and many municipal governments are not resourced well enough to have anything like this level of professional expertise on hand for the endeavor.
What TIFs and Stagflation have in common is the major risk in any "betting against the future" (really it's borrowing against the future, you're betting the future is good for you): You really need to know what you're doing, and be working with good data - which, when talking about the future, means making sound assumptions. This is often as much art as praxis.
Public spending in developing countries at almost all states of development from early development in places like Africa, to later cases like some southern European countries (Portugal, Italy, Greece and Spain) is often not fruitful, and often leads to a foreign debt crisis requiring austerity measures that are painful to members of the public and are often economically dubious. When borrowing for public expenditures goes bad, it is called a "debt crisis."
The Encyclopedia Britannica notes many examples, including "the Latin American debt crisis of the 1980s, which resulted in a “lost decade” for the region, and the European sovereign debt crisis beginning in 2009."