TITLE: Can Nash Equilibrium be more than two?
QUESTION [9 upvotes]: In the Prisoner's Dilemma example, we know that there is only one Nash Equilibrium.
That is both of them confess. 
Is it possible that there are two Nash equilibriums in one example?
Can you roughly give me such an example?

REPLY [2 votes]: A bit late to the party here, but you can indeed have two Nash equilibria.
$$ \begin{array}{|c|c|c|} \hline
  & L & R \\ \hline
T & 1,1 & 0,0 \\ \hline
B & 0,0 & 0,0 \\ \hline
  \end{array} $$
Here there are precisely two (pure) equilibria, even if one allows for mixed strategies: $\{T,L\}$ and $\{B,R\}$.
A bit more in-depth, for a 'generic' finite strategic-form game (for our purposes, generic = games without ties in payoffs), you will always have a finite, odd number of equilibria.  In fact, when you have weirdness like an even number of equilibria, it usually means one is not 'stable' in some sense.  Here, $\{B,R\}$ is the 'theologian's equilibrium': if you're playing it, you best have total faith your opponent is playing along as well.  If you have any doubt, then there's a better alternative.
Depending upon your background/interest level, another way of explaining the weirdness of the above example is to note that $\{T,L\}$ trembling hand perfect, while $\{B,R\}$ is not.