Thanks everyone who responded!
I guess I was thinking about this topic because during the summer of 2014 I achieved a milestone amount of financial assets which, ignoring deferred tax liabilities, would make me FI at a barebones level (though my current spending is higher due to discretionary items I value).
Realize expenses as they occur. Plan out cash flow projections for FIRE re: 4% WR.
If we are to realize expenses as they occur, when do they occur? I think it's implied in your quote that the expense occurs when you sell (is that a fair reading of your quote?), but I'm not sure I'm sold on that. The alternative view is that the expense occurs when the securities appreciate (creating an unrealized gain), and I think this is the view that GAAP accounting for businesses takes, that companies are required to record deferred tax liabilities against deferred / future / unrealized income. I am personally pretty firm on the accounting theory that expenses can occur in a different period than a cash outlay.
Now, personal finance accounting is not business accounting, but I'm not sure why we should think about this particular topic differently. On the other hand, I am clearly in the minority of opinion, judging not just from responses to this thread, but from the searching I did for similar threads (before I started this one); none existed.
I could see how it might be useful to do this exercise to estimate your projected net worth in the future, but including it in calculating your present-day net worth feels incorrect to me. Wouldn't it be like subtracting all the remaining interest from a mortgage amortization table right now, or including a present asset value on the future benefit payout from Social Security?
I am not completely sure I understand this question: "Wouldn't it be like subtracting all the remaining interest from a mortgage amortization table right now[?]" - I think future interest expense should be excluded from your balance sheet / net worth calculation. Your balance sheet should include the principal balance of your mortgage only - whatever you could pay it off today for. If you don't pay it off today, then the projected interest expense from the table becomes actual interest expense, but not before.
As to the second point regarding the present value of expected Social Security benefits, I would just advise people to be conservative. I'm not one to make predictions about future acts of Congress regarding individual programs, but in general, the "haves" get taxed to provide for the "have nots." If you are reading a pedantic discussion on an early-retirement-focused personal finance message board regarding whether to include certain minutiae in your personal net worth calculation, then you are most likely a "have."
@slugline, I intend to pay very little tax after I FIRE. However, if suddenly my job collapsed, and then I had a stroke and had no disability, and then etc.....I think it might be valuable to know exactly how much cash I actually have net of all commissions, taxes, penalties, etc if I had to cash it all out at once. That's kind of what I thought I might use something like this for. Unlikely scenario, but easy to figure out and it couldn't hurt to know.
So I see more value in doing this on today's NW than I do my post FIRE NW, since I will be able to manipulate the way I liquidate then.
I think this is helpful. Thanks.