The Smallville series finally closed in May 2011, ending its tenth season and 10-year run. Personally I think the show was too overdue. I stopped watching it a long time ago despite being an initial enthusiast. However, I would still like to discuss what took place in the first three seasons.
TV shows use sex to sell, and Smallville is not an exception. Well, it would indeed be a waste with such an eye candy leading man like Tom Welling. For the first three seasons, Lois Lane - Clark's destined partner - hasn't even been introduced. But the show does not lack juicy elements.
Clark has simultaneous sexual tension with his best friend Chloe and girl-next-door Lana Lang. Both of them are alluring: the former smart and adorable, the latter beautiful and vulnerable.
Nothing even happened between Clark and Chloe (despite many compromising scenes like this one) because the feelings came only from Chloe's side. For Lana, what constantly stood in hers and Clark's ways were his secret and her various suitors (Smallville wikia). Even when they express their feelings for each other, Clark's super power makes consummating their relationship problematic.
An older blogger from Cheap Sex and Other Stories observes, Lana and Clark have a problem that is similar to that of Edward and Bella:
If he's 'faster than a speeding bullet/more powerful than a locomotive, then surely his ejaculate would shoot right up and through her. Killing her.
Cleverly enough, the writers arrange for them to have sex during the time Clark loses his super power in season 5. They actually lose their virginity to each other, which is really sweet (and quite unrealistic considering how many boyfriends she's had). Later on, they are able to do it again when Lana gains super power. And their combined strengths render seismic tremors all around town - just a superman version of rocking the bed.
In my opinion, the series progressed too slowly, leaving the sexual tension between these two unresolved for seasons. And it isn't just the tension that keeps the audience on edge. Their on-and-off relationship was also constantly stormy until her tragic death in season 6. I understand that the producers have to employ this tactic to keep the show going for 10 seasons. However, it's quite ineffective in keeping a loyal audience interested in the long run.