I noticed that even when Ian/Lena commit to a serious relationship, if they don't go all the way (if you limit it to oral sex), then Ian can't complain later when Lena cheats on him with Mike/Mark/Jack, etc. It's like he gets emasculated and she's in total control. Even when Jeremy tells him that she's cheating, he does not confront her about it at the beach house. It's very interesting in that it becomes an open relationship type of thing if they fail to have vaginal sex. She even dictates that they should have a MMF threesome.