I'm not worried about indices going into a bubble relative to other stocks, but I'm worried that the mainstream investing advice is now along the lines of "invest in an index, the market always goes up in the long term, you can't go wrong with an index if you hold during the lows, etc." which is only based on historical data where this advice wasn't present, and creates a surplus of money in the stock market (demand >> supply).
Historically, when there was a downturn, people were afraid, sold in masses, started working to get back on track, etc. but I wonder if with this newfound wisdom, people would just keep buying during lows, so there won't be lows anymore, and "holders" will lose their comparative advantage since there won't be any more "suckers" / losers in the game... nomsayin?