It's interesting to use this reasoning in the context of tax-avoidance that the parent mentioned. Would you rather have $[some_large_number] of cash, or $[some_large_number + some_large_numer*(tax rate)] in [tech stock]?
Really, stepping up to an even higher level of abstraction I think the most important advice is to pay attention and think about your options. I think that far to many people fall prey to inaction and sticking with the status quo simply because it is easier.
It's far from obvious whether it's better to be 25% poorer with diversification.
Unless you think the tax rate is going to be lower in the future, once you've hit the long-term capital gains threshold, I don't see a reason to believe that paying taxes now and switching investments is worse than holding investments and paying all the taxes later.
[1] http://www.boe.ca.gov/proptaxes/faqs/propositions60_90.htm#1