Why do both stock and bond seem overvalued in 2014?

Question

The general wisdom is that when stock is overvalued, bond is undervalued, and vice versa. Why are both suggested to be in a bubble in 2014? Also, if one believes in tactical allocation, what asset should be over-weighted in this situation?

UPDATE:
In response to comments, for example, this author writes in the Economist (2014 May):

as oft mentioned here, the Shiller p/e is well above average in the US, nominal junk bond yields are at record lows and some European government bond yields are at remarkable levels; Deutsche says the Dutch bond yield is within a whisker of its lowest level since 1517! [...] What we have is a very odd market, in which volatility is extremely low, and economic optimism seems high as judged by the equity market but not by the bond markets, emerging markets or commodity prices. It may all bear out Pimco's thesis of the new neutral - that rates will stay low for longer. That would explain why equity markets can be near highs, while bond yields are falling

I think it's generally accepted that at least based on historical indicators, stocks and bonds are valued very high at current prices/yields

Answer 1

Bonds are priced "very high" because their price is compared to their yields. With the current interest rates, which are very low, the bond yields will be low. However, bond issuers still need the money, so there still will be high par value, and investors will not sell bonds at a loss unless there's a better investment (=bonds with better yields).

Once the rates start going up, you'll see bonds with current rates dropping in value significantly. Once alternatives appear, people holding them will start dumping them to move the money somewhere more profitable.

Similarly the stocks - since there's no other investment alternatives (yields on the bonds are low, interests are low), people invest more in the stocks. Once the rates go up, the investors will start rebalancing portfolios and cashing out.