I'm wondering if a few of you would be willing to share how finely you decided to slice your pie, and why you made the choice you did.
Before I answer the question, I should point out that our biggest asset class is our military pensions. We can do a lot of experimentation while knowing that we'll always have enough money for groceries & property taxes.
I don't know how to account for our rental property. This year it turned a considerable (taxable) profit, but that could be just deferred maintenance or the gap between hurricanes. I don't think you can "rebalance" rental property unless you have a lot of it, and in our case we're holding it mainly for family convenience instead of investment return. I hope to answer that question for good within the next two decades... hopefully our exit strategy is not "probate".
Having fronted those disclaimers:
Frank Armstrong used to call it "diworsification". It's a necessary part of investing, but it's too easily taken to extremes.
I can handle the tracking on a half-dozen assets. More importantly, I can only ignore the tracking on a half-dozen assets without eventually getting bitten by one of them.
I know that some can keep tabs on a portfolio of 30-40 individual stocks, but I think that you have to be hard-wired to stay up with the tracking. Otherwise I'd get a few weeks behind and suddenly I'd have a part-time job updating my portfolio. I found it was a chore just for a dozen individual stocks, let alone a meaningful number.
I've also spent a considerable amount of time over the last 30 years experimenting with different asset classes. You can buy just about anything and claim that you're experimenting with it, but you don't get a real feel for your emotional tolerance on a class until it's at least 10% of your portfolio. There's nothing quite like the thrill of buying on margin, shorting, or selling naked puts, and I don't mean that in a good way. But I didn't really know whether I'd find it worth my time until I tried it and scaled it up. Those criteria of "How do I want to spend my time?" and "Can I sleep at night?" helped me decide to stay away from commodities, most bonds, peer-to-peer lending, IPOs, and all but one individual stock. So I'd say that any asset in a portfolio should make up at least 10% of that portfolio.
Like Clif, I've made angel investments in startup companies. I've spent five years getting into it, and I'll probably spend 5-10 years getting out of it. The process has been hugely educational and it's made me a better investor. The "problem" is that it has not yet been profitable. (Even rental real estate is more liquid than an angel investment.) More importantly I've learned that I have "enough". If I end up sitting on the next Google or Facebook, I don't think it'll make a difference in our lives. Same with the income from selling call & put options-- it's not profitable enough unless you scale it up, and then it's too much risk for the work.
The biggest advantage of all this experimentation is that I won't be tempted to try any of it when I'm in my 70s or 80s. I'm apparently at the peak of my cognition right now, and it's all downhill from here. 25 years from now when some nice young man (or sweet young girl) cold-calls with a can't-miss idea, I can probably say that I've been there and done that.
In our ER portfolio, our top three are the Dow Dividend ETF (DVY), the International Value ETF (EFV), and Berkshire Hathaway. Small cap is close behind, with shares like the iShares small-cap value ETF (IJS), the TSP "S" fund, and angel investments*. These days we try to limit each to 18-28% of the portfolio before rebalancing.
We usually try to keep our cash fairly low at 4-8% of our portfolio just because it's two years of living expenses. Right now we're sitting on an all-time high of 15%, but I suspect we'll have a few opportunities to put some of that to work in the coming year.
*
Yeah, I know angel investments are in a class by themselves. But by lumping them with small cap, I'm forced to sell one to buy the other.