The theme of this episode was about power, and its source and who's in charge and so on. In the book, the political story was Tyrion trying out-maneuver Cersei in order to have them both survive their common enemy in spite of her blunders. From almost day one, the show appears to have gone a little too far to give Cersei more credibility than she ever deserved, and her scene with Littlefinger might give the typical shallow viewer the impression that she is more shrewd and in touch with the realities of politics than she really is. If they are going to continue making Cersei seem competent (note that they cut out her admission of how close she came to losing to "honorable but dumb" Ned, if not for Sansa's betrayal), then the ineptitude that Tyrion must struggle against has to come from another source - hence Joffrey's greater measure of power in relation to Cersei. Also, it's easy to understand in the books the balance of power. If Cersei is in charge, the audience will have trouble wondering how she can lose control of Joffrey and how she is still, to a certain extent, subject to the illusion of his rule. With the characterization of the books in mind (and recalling Littlefinger's sexposition monologue near the end of last season), it might seem like Cersei has the upper hand and put Baelish in his place, but the truth is, she simply demonstrated the limitations on her own understanding of power. Yes, this is the guy who manipulated the outbreak of war between the Starks and Lannisters and (theoretically so far) induced Joffrey to destroy any hope of a resolution of that conflict by killing Ned, but he is also capable of being killed by Cersei at the drop of a hat, yet she does not even understand the point he makes to Sansa in aFfC when he points out that she really has no power of her own. That power she flaunts to Littlefinger is the sort he has never had, but she is only borrowing it herself, from her father, husband and son. As a result, he is far more adept because he has had to develop his own power while she is vulnerable to its loss at the source.

At the end, we know Littlefinger's ability to manipulate is undiminished, only now he is forewarned about Cersei's own capability for precipitous action and lack of respect for his power, while Cersei has just been given a rude awakening about how little power she really control in her own right. And if the show carries on the unspoken assumption from the books - Littlefinger has already proved capable of manipulating the very guy who yanked Cersei's chain short. They can take that scene and use it to spin all sorts of motivations and explanations of Pety's upcoming schemes and actions in regards to Cersei.

I was not fond of either of those scenes myself, but within the limitations of the format, it might turn out to be useful in setting up other stuff. Not least, the bastard massacre at the end. In the books, it was a clear sign of nothing more than Cersei's vicious nature, whereas one TV critic on his blog seemed to believe it was a somewhat necessary action to choke off future challenges to Joffrey's claim. Anyone familiar with the books would realize exactly how absurd that notion is, given the extreme marginalization of bastards, and how even a couple of different places where a king tries to arrange for a bastard successor, it comes to naught. That massacre was not the extremes Cersei will go for her children, it was an illustration of the depth of her hatred and pettiness towards her husband, and perhaps in the context of the episode, an act by which she can feel powerful again.