Stupidity: Lance and Lana's actions at the end don't make sense, other than to set up conflict for the plot. Lance won't give Lana a shot. Lana steals a vile and after Lance injects Lex (to stop him, fine), he finds Lana, who is trying to inject herself. He stops her, throws her back, then proceeds to try and inject her. He could have just waited and let her do it herself, or taken the vile and left. Lana is then scared that Lance is about to inject her when that's what she wanted in the first place.
Stupidity: When Clark is trying to sneak Lana out of the house, they walk past the front door in order to go through the kitchen door, where they get caught. It makes no sense to not use the front door. This way Lana is already outside, the whole goal in the first place, should his mom or dad see them. Not to mention the fact that Lana's car is still parked outside and Johnathan or Martha would have seen it, so they shouldn't be surprised to see her in the house.
