An odd thing about
The OC is how externally driven its plots are. It seems that most of the conflicts come from recurring characters interacting with the core cast rather than the core cast interacting with each other. For example, Trey is the latest in a long parade of recurring characters coming out of someone or another's past: Ryan's ex-girlfriend/mother of his child, Rebecca, etc. Yet they've never done an episode where Sandy pays more attention to Ryan than he pays to Seth, and yet that's an obvious one: from the beginning Sandy made clear he used to be like Ryan. You'd expect that at some point he'd gravitate to the kid he understands better, and that Seth might feel threatened.
Various people have remarked how fast
The OC burns through plot territory, lacking triangles, as it does. Is it that they don't trust that their core cast are interesting enough? But there's no way to make them interesting enough if you don't give them their own plots!
To paraphrase
John Rogers, they're really sucking on the recurring character crack pipe...