No value or missed value bet on river?

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Party Poker 2/4 Hold'em (10 handed)

Preflop: Hero is SB with A/images/graemlins/diamond.gif, 9/images/graemlins/spade.gif.
UTG calls, <font color="666666">1 fold</font>, UTG+2 calls, <font color="666666">3 folds</font>, CO calls, <font color="666666">1 fold</font>, Hero completes, BB checks,

Flop: (5 SB) 4/images/graemlins/spade.gif, 6/images/graemlins/club.gif, 8/images/graemlins/spade.gif <font color="blue">(5 players)</font>
Hero checks, BB checks, UTG checks, <font color="CC3333">UTG+2 bets</font>, CO calls, Hero calls, BB folds, UTG calls.

Turn: (4.50 BB) A/images/graemlins/heart.gif <font color="blue">(4 players)</font>
<font color="CC3333">Hero bets</font>, UTG calls, UTG+2 folds, CO folds.

River: (6.50 BB) 3/images/graemlins/heart.gif <font color="blue">(2 players)</font>
Hero checks, UTG checks.

Final Pot: 6.50 BB
<font color="green">Main Pot: 6.50 BB, between Hero and UTG.</font>

My thinking here is UTG is on a straight or flush draw because there is a good chance he would bet out with a pair of eights or c/r the flop.
I gain nothing by betting the river if UTG's straight or flush draw got busted.
If UTG made his straight on the river, the bet costs me 2BB.
Not to mention I could be behind an ace. The only ace hands I can beat are A-7, A-5, A-2. Any other ace may very well cost me 2BB.

Correct line of thought?

[PassiveCaller]

I like the thought but it comes down to your opponent. Is there any read here. could he have something like 67s or 45s as well? Against a decent playing opponent there isn't too much value here though as you've noticed but against the more fishy I think you should still bet this.