Poor play by me, what about by him?

[Thebram]

I realize I made a few mistakes on this hand, but my specific question is about CO's play.
In this specific instance, it worked out well for him. But in the long run, it seems like giving this many free cards is a poor play.

He had been playing pretty tightly and passively. So I know my river call was bad, since the pot was so small, and he probably wouldn't raise with anything I could beat.

Anyway, here's the hand.

Party Poker 0.50/1 Hold'em (9 handed) converter

Preflop: Hero is BB with T[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/spade.gif[/img].
UTG folds, UTG+1 folds, MP1 folds, MP2 folds, MP3 folds, CO calls, Button folds, SB folds, Hero checks.

Flop: (2.50 SB) 5[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/heart.gif[/img] <font color="blue">(2 players)</font>
Hero checks, CO checks.

Turn: (1.25 BB) T[img]/images/graemlins/diamond.gif[/img] <font color="blue">(2 players)</font>
Hero checks, CO checks.

River: (1.25 BB) 2[img]/images/graemlins/spade.gif[/img] <font color="blue">(2 players)</font>
<font color="CC3333">Hero bets</font>, <font color="CC3333">CO raises</font>, Hero calls.

Final Pot: 5.25 BB

Results in white below: <font color="white">
Hero shows Th 7s (one pair, tens).
CO shows Kc Kd (one pair, kings).
Outcome: CO wins 5.25 BB. </font>