In response to the case against QQQQ, a reader wrote a cogent argument for why QQQQ is a useful and usable ETF for long-term investors. Here it is:
I'm writing a counter-argument to your point about QQQQ, and see if it ropes anyone else in to discuss this. My counter-argument has the following parts:  Fundamentals,  Correlation to the S&P 500,  Liquidity,  Inclusion policy.
This part argues that QQQQ may be appropriate not just for the trader but also for the long term investor.
In principle, you're absolutely right: the exchange on which a stock trades seems like a silly criteria to base an ETF on.
But in practice (perhaps purely by chance!) QQQQ happens to be a great collection of stocks that represents a slice of the future of America (actually more than just America; there's some international exposure also).
In other words, by coincidence QQQQ happens to contain most of the stocks my fundamental analysis (bias toward Growth) says I should own! Yes it's got Microsoft, Intel, Qualcomm, Apple, Cisco, and other tech, but it's also got Starbucks, Whole Foods, Bed Bath & Beyond, Costco, Dollar Tree, Amgen, Genzyme, Celgene, Paccar, Comcast, Sears Holdings, Pet Smart, Fastenal, Pixar, generic drugs, a casino, satellite radio, and more.
You make mention of the fact that it's tech-heavy but does not contain HPQ or IBM. Again, perhaps purely by chance, the example is illustrative. I don't want HPQ and IBM. I want DELL, INTC, AAPL, and one of the outsourcers (e.g., Congnizant).
And (again, coincidentally) I like that it does not include Oil and Financials because I prefer to hedge with those separately.
So for my philosophy, the mix contained in the index happens to work out, but I realize that it may not for other fundamentals-oriented investors.
That said, I'm not totally happy... I would love for QQQQ to include GE, and a couple of others. But see point , "it's close enough".
 Correlation to the S&P 500, but with a higher beta
Of course, if I had to choose 100 stocks individually, I cannot say that I would buy every single one of the 100 stocks in QQQQ, and in those proportions. But this is true of buyers of any large basket of stocks. Buyers of such baskets are looking for broad exposure to American industry, and it sounds funny when you say it, but the small details (fringe stocks of which there is a tiny percentage of in the basket) don't really matter. It's close enough! QQQQ has very good correlation to the S&P 500, and I think that that's what's important. It has a higher beta. I believe this to be a benefit to me, because part of my philosophy relies on market timing. The higher beta lets me get in at lower lows and out at higher highs.
The extreme liquidity of QQQQ is a benefit. Part of my philosophy relies on rebalancing frequently and taking advantage of overreactions by the market, and QQQQ makes that easier by reflecting traders' emotions faster than less liquid ETFs.
 Inclusion and exclusion policy
I like the clinical inclusion policy. The index is reviewed every quarter and the top 100 capitalized non-financial stocks on the Nasdaq make it in. When a company in the index becomes smaller than the 125th in market cap, it is dropped and the new 100th is added. I like clinical objective policies (even though they may become somewhat random in the corner cases) and thus prefer this to more subjective ones in other indices.
I know there are disadvantages to market cap weighted indices, but I do think there is a correlation between success and market cap. The objective inclusion policy should result in early detection of failure or diminishing success.
I think that those things combined makes QQQQ more appropriate for me than SPY or IVV. Would love to discuss this further with others on this site.