se no one builds such assets knowingly! But asset valuation, always difficult, was often being driven to distraction by stock market bubbles, inflated demand forecasts, igno- rance of other new competitors, and valuation formulas that were more likely designed to make investors open their pocketbooks than to deliver a true answer. Assets can be valued in different ways, of course. One approach is to look at book value: Take the amount invested and subtract depreciation. This works for tax purposes, but it makes no attempt to balance supply with demand. Its main benefit is simplicity. Investors do not, however, shell out cash because they will just end up with book value. Another metric is enterprise value: Look at a business' revenues and profits, apply some time-value-of-money metrics, and determine a net present value. That is usually much closer to what a business is really worth. But it has much more room for error, because it depends on pre- dictions of the future. During the boom years, entrepreneurs often got help from industry analysts who willingly exaggerated future demand. This provided higher forecasts for future profit, giving their plans a higher enterprise value. And at the end of these multiyear profit forecasts, enterprise valuation for- mulas include a terminal value, typically a multiple of forecasted revenues, based on the assumption that a stable, mature company's value can be approximated that way. So if a business was forecasting 10 years of high top-line growth, its terminal value could be extremely high, and thus the net present value (that is, with the estimated future value discounted for the time value of money) could still be dominated by that top-line forecast. Valuations depending only on realis- tic future profit would have been lower, of course, but they were not fashionable during the boom years. Many investors did not even think about valuation in any kind of normal sense. During the dotcom boom, the most flagrantly overvalued companies, such as Web site operators, were frequent