While I agree that the plot was lame in season 3, I had to keep reminding myself that the plot isn't what this show is about...it's the characters. The show is one giant, intertwined series of character studies. The plot only exists as the catalyst that brings all these unique, unrelated characters together. For that reason, it's unlike any TV show ever created.
With that said, it all got a little too silly for me this season with the cult, the panties, the unionizing, and the missing heroine. Overall, there seemed to be too many plot lines going this season to flesh them all out properly. A TV show must still be entertaining and make relative sense, even if the plot isn't as important as the characters. Hopefully those aspects will improve with season 4.
A major theme with this show since the beginning is that in prison, people come and go. Out of seemingly nowhere, new inmates show up and old inmates abruptly go away. In reality, that's probably an accurate portrayal of prison life. However, now it seems they've decided to do that with plot lines as well.