what's the point of semibluffs?

[jsnipes28]

PP 100NL Full Ring, full stacks
Hero is MP 4 [img]/images/graemlins/diamond.gif[/img]5 [img]/images/graemlins/diamond.gif[/img] 2 calls, Hero calls, CO minraises to $2, Button raises to 4, SB calls, BB calls, UTG calls, MP1 calls, Hero calls, CO calls.
Flop: K [img]/images/graemlins/diamond.gif[/img] T [img]/images/graemlins/diamond.gif[/img] 7 [img]/images/graemlins/spade.gif[/img]
pot~$25
BB bets $15, he has been showing down horrible hands lately so i don't expect a monster. UTG folds, MP folds, Hero raises all in $100, everyone folds, BB lets his clock expire and then calls.
Turn: 6 [img]/images/graemlins/diamond.gif[/img]
River A [img]/images/graemlins/club.gif[/img]
BB wins $240 with a flush Q [img]/images/graemlins/diamond.gif[/img]3 [img]/images/graemlins/diamond.gif[/img]


Same table, after swearing i would never semi-bluff again...
Hero is CO with 7 [img]/images/graemlins/diamond.gif[/img]8 [img]/images/graemlins/diamond.gif[/img]
UTG limps, MP raises to 3, MP2 calls, CO calls, Button calls, SB calls, BB folds, UTG calls
pot~$17
Flop: 10 [img]/images/graemlins/diamond.gif[/img] 6 [img]/images/graemlins/diamond.gif[/img] 5 [img]/images/graemlins/heart.gif[/img]
Crazy [censored] bets 5, Hero raises to $20, Button raises to $50, Crazy [censored] calls, Hero pushes $80, Button runs down timer and then calls. Crazy [censored] calls.
Turn: A [img]/images/graemlins/heart.gif[/img]
River: K [img]/images/graemlins/diamond.gif[/img]
Button wins $300+ w/ flush A [img]/images/graemlins/diamond.gif[/img] 3 [img]/images/graemlins/diamond.gif[/img]
Crazy [censored] shows 10 [img]/images/graemlins/heart.gif[/img] 6 [img]/images/graemlins/spade.gif[/img]

Are these terrible pushes on draws. I assumed that you had equity against better draws, but apparently this is not the case. At this limit, do you guys find yourselves being called by better draws when you make these types of plays. I'm just completely befuddled because i know that i am playing horribly, having lost $700 this past week, but i don't feel like i'm playing too terribly. Could someone please help me out. I'm taking a week off, but while i am not playing i want to try and absorb as much info as possibly. I just don't want to end up 4 tabling full ring being a nut peddler. Thanks for all help advice, and especially criticism.