> Not true; if housing prices continue to increase, then even without rent it becomes a reasonable investment.

Only if other investments with the amount of capital needed for housing don't produce better results and you can guarantee that there will be buyers of the property post appreciation. There are very few (but they are there) housing markets where real estate has appreciated faster than stock markets or other asset classes and can offset taxes in selling the home. If you're using housing purely as an investment vehicle there's also the risk of a downturn causing real estate prices to decrease due to the low liquidity of housing (compared to, say, a fund).