Unreadable opponent, or just stupid?

Ok so I usually sit around here late at night playing on Pokerstars playing in at most the small .25/.50 tables. It may not seem like much to some of you but oh well. Anyways, here lately I havent been able to catch a break, actually Ill go as far as to say im getting screwed over now that my bankroll is up. Anyways, I came across many players that were just making unbelievable calls/raises. Here is an example of 1 hand that just blew my mind a minute ago.

PokerStars No-Limit Hold'em, $0.50 BB (6 handed) converter

UTG ($15.25)
MP ($13.95)
Hero ($3.50)
Button ($30.95)
SB ($18)
BB ($11.40)

Preflop: Hero is CO with 8[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/heart.gif[/img].
<font color="#666666">1 fold</font>, MP calls $0.50, <font color="#666666">2 folds</font>, SB completes, BB checks.

Flop: ($1.50) 4[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/spade.gif[/img], T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, BB checks, MP checks.

Turn: ($1.50) T[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets $4.5</font>, <font color="#CC3333">BB raises to $10.9</font>, MP folds, SB calls $6.40.

River: ($23.30) 7[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>

Final Pot: $23.30