Keynesians both on this board and IRL always say they'll cut back spending once good times come back, do you believe them?
Economists don't deserve the blame. Politicians and voters deserve blame. It's not like economists hold guns to the heads of politicians and demand spending. It's voters who demand spending. The economy is great! Let's spend record amounts of money so we don't have a rainy day fund! Look at the current situation. The economy is absolutely booming, unemployment is down, retail is doing great, American businesses are not going bankrupt at a record pace, and Obama has fixed the economy, but we're still looking at trillion dollar budget shortfalls. This is insane. If this is the budget during prosperous times, imagine what it looks like during a recession. We'll have the same spending, but tax revenues will be down.
Economists are not the bad guys. Keynes could easily be described as intelligent and prudent. His theories make perfect sense, but nobody wants to try them. Save for a rainy day - we never do that. Only use your rainy day fund (or printing press) when it's actually raining - we don't do that. We're running the printing press at full blast even when unemployment is below 6%. Today, Keynes would be considered a hardcore right win tea party conservative.
The problem is that people are lemmings. I can't remember who said it, but someone said the memory of investors is about 2 years. Past 2 years, nobody remembers anything. Nobody remembers how the 1980s were almost exactly the same as the late 1990s. It was the new computer age, this was the new economy, earnings don't matter, clicks per dollar, leveraged buyouts funded by junk bonds. The stupidity of humans is so reliable that you can read almost any investing book written in the last 100 years and you can't tell when it was written. You could read a book written in 1920 and it would describe pretty much every bubble you've seen in your life time. It's always different this time, it's always a new age. We never need to save for a rainy day because rainy days will never happen in the future. The future will never have recessions again, stocks will always go up, real estate will always go up, it's always a good idea to spend record amounts of money during the boom times instead of savings it for the bust times.
Keynes assumed humans are not completely retarded, and that was his mistake.