I think you know there's a bubble when people tell you about the stock picks (amateurs and professionals), and when you quiz them about why the bought, they giv

I think you know there's a bubble when people tell you about the stock picks (amateurs and professionals), and when you quiz them about why the bought, they give you irrational arguments i.e. things unrelated to future cash flow. The reasoning for buying current tech companies may be forward looking or optimistic, but it's not irrational.