Explain to me why this might be bad

[ajmargarine]

BB: $307.95
UTG: $19.35
CO: $302.20
Hero (BTN): $191.70
SB: $177.70

Pre-Flop: 4[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/heart.gif[/img] dealt to Hero (BTN)
UTG folds, <font color="red">CO raises to $6</font>, BTN calls $6, 2 folds

Flop: ($15) 9[img]/images/graemlins/heart.gif[/img] Q[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/club.gif[/img] (2 Players)
CO checks, <font color="red">Hero bets $8</font>, CO calls $8

Turn: ($31) 4[img]/images/graemlins/spade.gif[/img] (2 Players)
CO checks, Hero checks

River: ($31) J[img]/images/graemlins/heart.gif[/img] (2 Players)
CO checks, <font color="red">Hero bets $23</font>...

Assume unknown villain (who is multitabling tho)