A couple of limitations: minimum purchase amounts and transaction costs.
I agree with what most of you have posted, especially for boosting returns. Ideally, I'll end up with a small basket of indices, including ones who are more Growth oriented, to skew my returns upwards*, because as well all know historically small caps have given a 20% premium on returns over big caps.
(* That's what IFA/DFA does, but I don't have the 100 K$ minimum account (and won't have for a quite some time either).)
Long story short, I also can't market-time shit. I know the US represents roughly half of the world's stock market capitalization. But one year it's the USA, the next it's Mexico, the next it's Lithuania, etc.
Call it too simplistic, but I see this as a whole. To quote a chemist, "Nothing is lost, nothing is created, everything is transformed." ... or more aptly "everything changes hands" with regards to money. Since I can't market-time, and guess what the next big thing will be, I thought I'd just buy the whole enchilada ... for starters.
Sure, I won't get stellar nor dumpster returns, but for now I can live very well with a 10 year 11.60% average (Vanguard VHGEX) return. Either I dollar-cost average it, add indices one at a time (and feed the laggers), or buy sub-sectors to augment concentrations ... all will depend on future cash flows.
Thanks! Currently searching for something similar on the fixed-income/bonds part of the porfolio. My 'gamble' money is in the world indices, but the 'safe' part must get higher returns than money market funds.
What a hobby!