The popularity of iCarly and its influence on younger fans can not be denied. Indeed, its reach is so widespread that even those in their teens and twenties who don't like the show use terms that originated from it ("chizz" and "jank" being two of them). Because of this, I take how iCarly portrays friendships, romance, and the underlying messages thereto very seriously. This is the primary reason I have strong reservations about series' portrayal of the main pairings, Creddie and Seddie.
Before I tackle that, I must say that the fan fiction writers often have certainly thought deeply, coherently, and honestly about the ships - even when writing straight wish-fulfillment fluff. Indeed, many FF writers routinely do a better job of handing these issues than the show's actual writing staff has done over the years. Many fans have use the series as a vehicle to explore issues that real young adults must deal with in a very thoughtful way.
However, IMHO, the fans of each ship are also far too forgiving of their ship mates' foibles when viewed in the context of the ship. For instance, Creddiers find Carly's manipulation of Freddie via, "Please, for me" as cute rather than mean. Similarly, Seddiers believe that Sam's mean-spirited bullying is her way of coping with her affection for Freddie. Conversely, when it comes to the other ship, both are blind to the obvious plusses of the other, such as Seddiers believing the Creddie kiss in "iGoodbye" was meaningless or Creddiers downplaying Freddie asking Sam if she wants to go back out with him in "iGoodbye." In fact, both don't point the finger at who is the offencive party here (Freddie) because each has a vested interest in that character's integrity and affection.
It is because of this that I find the handling of Creddie and Seddie at the end of the series to be risible. If these characters were real people, then: Freddie has no right to tell Sam that only Carly likes him in "iStill Psycho"; Sam should not openly flirt with Zayne in "iGo One Direction"; Freddie should not lie to Sam about his crush on Carly returning in "iOpen a Restaurant"; Freddie should not bad-mouth Sam to her superior in "iPear Store"; Sam should tell Carly about Freddie asking her back out in "iGoodbye"; Carly should tell Sam about the Creddie kiss in "iGoodbye." Frankly, with that track record, NEITHER Carly nor Sam would be smart to date Freddie until he gets his head screwed on straight. If someone had done that to one of my sisters, I would have wedgie bounced him while beating him senseless with a butter sock until his brain turned into pureed guano.
What is worse is that pre-teens, teens, and twenty-somethings have taken this behaviour to heart. Carly basically took Freddie for granted for years while using him, so it's OK to do that to people you know. Sam was forgiven by Freddie for her abuse and bad-mouthing, so it's OK to do that to people you know. Sad, but true. That's just horrible. Their pasts should impede all of their romantic relationships within and outside the trio.