Okay first up, Pam, Eric's offspring and assistant at Fangtasia. She's been making Lafayette sell vamp blood under Eric's orders. If she gets caught the Magister might put her on the chopping block. I hope it isn't her and I doubt it since they have finally introduced her as a main character and not just a sometimes there person. I also really like Pam.
Lafayette is next. Now in the books he died in the beginning of book 2 so he's already over his limit and he's pushing the blood. If he gets caught, I doubt they'll just torture him again.
Sophie Anne, the Vampire Queen. She's the one making Eric sell the vampire blood to fill her empty coffers. She needs cash fast and doesn't care how she gets it. Those who have read the books know her days are numbered but it is way too soon for her to die now. Still, she might be on the block.
Jason, Sookie's brother. Okay he's a jerk but I doubt he's going down. He provides too much delicious fodder through his sheer stupidity.
Sam. He's on a quest to find his origins and even though they are sleazy I doubt he's doomed. After all, if he goes where will Sookie work? And Sam is the only supe she has always been able to count on to help her out.
Lettie Mae, Tara's boozer mother who spouts off about Jesus every time she opens her mouth. I wouldn't mind seeing her bite the dust. She's a nasty piece of work.
Chow, Longshadow's replacement. All who've read the books know that in book 4 he dies. So he's a real candidate for a slightly early demise.
Tara, Sookie's so-called friend. In both the books and now the series Tara has been anything but a good friend to Sookie. Far too selfish and just plain nasty. Frankly, I'd like to see them knock her off. She doesn't add anything but pure spite to the show if you ask me.
So of course that isn't every main character but these are the ones I think are most likely in trouble. But if one has to go, I'd really prefer Tara and my second choice would be Lettie Mae.