Carly and Freddie are best friends, and have a very close friendship.
After Cam, I think Carly and Freddie have the closest friendship on the show. Carly and Freddie respect, trust and love eachother (by love, I mean platonic love, OK?). Freddie trusted Carly, and only Carly, with his secret in iKiss (he'd never kissed anyone), and even when Sam found out, Freddie didn't seem to think Carly had told. He trusted that Carly would keep her promise and not tell anyone. And then, when Carly found out about how Freddie hadn't told Carly about kissing Sam (in iThink They Kissed), she seemed really hurt that Freddie (and Sam) hadn't trusted her. Instead of trying to get a confession from Sam, she went straight to Freddie. I believe it was because she trusted Freddie to tell the truth. She trusted that Freddie would tell her if he and Sam kissed.
After all Freddie's done for Carly, I believe he deserves to get her.
Freddie kept holding on to the hope that one day, Carly would love him back. He did so much for her. He risked his life to make sure she wasn't hurt. He never broke down and lashed out at her for her rejection. He never grabbed her and kissed her. He was patient, and he was going to wait until Carly was ready for a relationship, no matter how long it took. After all that, I think he deserves to get what he's always wanted - a proper relationship with Carly.
Even though Carly could take advantage of Freddie, she never made him do something that would harm him or anyone else.
Carly's done her whole "Please, for me?" thing countless times. But I don't remember any time when she truely took advantage of him for bad reasons. She's never made him do something that would get him into trouble. It's always been something small, sometimes for someone else. She made him fake Sam's crush for Sam, not her. She made him change Jake's voice for Jake, not her. She made him ask Jonah to ask Sam out for Sam, not her. So, when you think about it, that whole "Please, for me?" wasn't often a selfish act.
Carly and Freddie are always prepared to help or defend the other.
When Sam makes fun of Freddie, Carly's there to defend him. Freddie will defend Carly. He wanted to beat up Carly's boyfriend because he was being a jerk. Carly and Freddie will do anything for eachother. It shows how much they care and respect eachother. How far they are willing to go to make sure the other is safe and happy. As I said above, Freddie risked his life for Carly's sake.