[WillMagic]

[ QUOTE ]
a free showdown raise is good when:
1) there is a chance you have the best hand
2)you have some outs to improve to the best hand (therefore if they call you can fire on the river and win 3 bets instead of 2, but if you miss you still only pay 2 bets for the showdown: same as calling down)
3)FOLD EQUITY, villass might fold a lowpair or a hand that has 6 outs against you.

[/ QUOTE ]

You forgot the part about either being able to fold to a three-bet or being three-bet so rarely that it doesn't matter much (this means < 3% of the time, not 10% of the time)

Will