Before season 6: Erica Durance revealed at Wizard World Philadelphia 2006 that character development with Lois is very tricky, considering her eventual relationship with Clark. "DC Comics has really clamped down on Lois. You can't do a dream sequence (with her and Clark) or any of that sneaky stuff."
http://operationpb.blogspot.com/2006...rgo-holds.html
Also before season 6: Erica Durance might be the sexiest Lois Lane ever to hit the screen (or so her internet fans would insist), but until now Clark Kent has never been allowed to kiss her. With Superman Returns in the pipeline, TV bosses decreed that Smallville couldn’t do anything that might upset the movie franchise. So it’s only now the film is out that Clark and Lois are allowed to let their romance blossom on the small screen.
"They really were trying to be careful what they did with Lois,” Durance comments, “because they weren’t sure how they were going to take Lois and Clark and their relationship in the early stages of the movie. So for a long time Lois could never kiss Clark, they couldn’t have a relationship, there were some specific things that could not happen, even in dream sequences"
http://operationpb.blogspot.com/2006...rgo-lifts.html
Again, before season 6. From Steve DeKnight's TWOP Q&A:
"Ah yes, the restrictions on Lois. When she was first introduced, our main restriction was that she could under no circumstances have any romantic relationship with Clark. Even if he were on Red K, no huggy no kissy no anything. This I believe still holds. Another restriction was that she couldn’t even have a scene with Lex. That has since been lifted, but I believe she can’t have any romance with him either. I'm not sure about the DP stuff, although I think there may be something about her not working there yet. As for backstory about why she’s so aimless, I’m not sure if that’s part of the master plan. To me she’s just a young hellraiser trying to find her way. Which hopefully she’ll do soon."
http://operationpb.blogspot.com/2006...trictions.html