Quote from tradestrong:
You'd invest all your money in the Nasdaq? I sure as hell wouldn't. Actually, you just verified indirectly precisely WHY you would be fine dollar cost averaging. You mentioned emerging markets that have made a killing. If you're properly diversified, you would be invested in those emerging markets.
Proper investing doesn't mean buying one index and one index only. It means buying across multiple sectors and multiple markets. The idea is to find markets and sectors that aren't correlated so that if one does implode (like tech in 2000 and the financials in 2007), then your relative exposure is small enough that it won't kill you. And the other hand, your strong investments will continue to give you gains.
The idea is to smooth your equity curve and reduce volatility. When one of your markets or sectors you are invested in gets choppy and toppy, and a bubble is forming, you move out of that market or sector and start dollar cost averaging into uncorrelated investments.
I'm not advocating buy and hold, dollar cost average in only one index and forget about it, or 100% passive investment and never moving any money to cash.
What I'm saying is that anybody with a solid understanding of correlations between markets, up to date research on the state of the current environment for that particular sector or market, and a well diversified plan, WON'T get crushed to the point that savings accounts become better investments.