NL50 - why is "bet/call, bet" a bad line?

[Ramana]

Villain is 21/9/3, small sample size.

Prima Network No-Limit Hold'em, $0.50 BB (6 handed) Hand History converter Courtesy of PokerZion.com

Button ($49.67)
SB ($6.04)
BB ($3.21)
Hero ($49.25)
MP ($37.52)
CO ($37.83)

Preflop: Hero is UTG with J[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises to $2</font>, <font color="#666666">1 fold</font>, CO calls $2, <font color="#666666">3 folds</font>.

Flop: ($4.75) J[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $3.21</font>, <font color="#CC3333">CO raises to $6.42</font>, Hero calls $3.21.

Turn: ($17.59) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $11</font>


Same villain, different board.

Button ($49.67)
SB ($6.04)
BB ($3.21)
Hero ($49.25)
MP ($37.52)
CO ($37.83)

Preflop: Hero is UTG with J[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises to $2</font>, <font color="#666666">1 fold</font>, CO calls $2, <font color="#666666">3 folds</font>.

Flop: ($4.75) J[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $3.21</font>, <font color="#CC3333">CO raises to $6.42</font>, Hero calls $3.21.

Turn: ($17.59) 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $11</font>

I'm lost in this spot. Is this line any good? Why not?

Second hand is fabricated, I want to know whether this line is dependant on the board texture. In the second example we assume that villain might have been semi-bluffing the flop and we want to avoid giving him a free card. I obviously play b/f turn, since I assume that he will push on a bluff or semi-bluff very rarely.

Unimproved should we always be in c/c mode on a blank turn after b/c on a dry flop?