1) Kima Greggs is shocked when she hears from McNulty how he and Freamon manipulate the "homeless murders" to get manpower and equipment to actually do real police work. After one day or so she tells Daniels about it. She soesn't even give McNulty a chance to fix it. After all the things McNulty has done for her and the trust that has been buit between them, I don't find that believable from her.
2) Even more strange, I find the behavior of Herc. First, he gives Marlo's number to Carv to run that drug boss down. A few weeks later, he betrays Carv and tells Levy about the wire on Marlo. I don't see anything causing Herc to change his mind.