It sounds like most of you are basing your hypotheses entirely off technical analysis. While I agree that technical analysis should be strongly considered, I am a big believer that fundamental analysis will win every time in the long run.
The last two big runs we had were in the very late 90s and then in 2007. In both situations the proceding recessions were a direct result of significant flaws in the market.
In the late 90s everyone and their brother was starting up an internet business. Companies were trading at ridiculous prices relative to their earnings and even their earnings potentials.
In the mid 2000s there was a serious lack of regulation with mortgage backed securities. When the housing bubble burst, mortgage backed securities (that were considered AAA in most cases) had a horrible price correction.
Until I see a significant economical flaw in the market, I see nothing to support a correction to the level some of you are suggesting.
I will go on to say that companies like Tesla and 3-D Systems had some good runs, but I expect a sharp pullback with both in the near future. Both are trading at their current levels because of hype rather than their fundamentals.