Hahahaha it is just because it approaches 100 years that the danger is here. Are you ignorant of market's cycle on big scale : the order is about 100 years !!!? And do you know that for talking about odd something must be reproducible: this means you must find among 30 samples of 100 years stock market something that has lasted so long: this means 3000 years of statistical data. So you make me laugh. Really astonishing : you merit to figure in the next "Memoirs of Extraordinary Popular Delusions of 21th Century" from Charles MacKay II
http://www.elitetrader.com/vb/showthread.php?s=&threadid=26238 
. BTW you remind me of the stupid crowd during the Missipi scheme:
"Marshal Villars, was so vexed to see the
folly which had smitten his countrymen, that he never could speak with
temper on the subject. Passing one day through the Place Vendome in
his carriage, the choleric gentleman was so annoyed at the infatuation
of the people, that he abruptly ordered his coachman to stop, and,
putting his head out of the carriage window, harangued them for full
half an hour on their "disgusting avarice." This was not a very wise
proceeding on his part. Hisses and shouts of laughter resounded from
every side, and jokes without number were aimed at him. There being at
last strong symptoms that something more tangible was flying through
the air in the direction of his head, Marshal was glad to drive on. He
never again repeated the experiment."
Quote from pisspotpete:
Uh, Harry, you might want to set your chart scale to LOG. Then you get a nice gentle uptrend - sort of like the US GDP!
Sorry, but your crash theory just won't fly, or at least it would be but a fleeting moment in most investing lives.
For reference please see "Triumph of the Optimists: 101 Years of Global Investment Returns", Dimson and Marsh.
After 100 years of uptrend, I like the odds!