Originally Posted by Brutus
Marie's thievery, in my opinion, was just a way for the writer's to stack up Skylar's struggle with everyone around her losing their moral compass. It sort of forced her to accept Walt's 'profession' a bit more because she couldn't stand on moral ground with her sister being a thief and her boss cooking the books. I agree that this wasn't all that enjoyable an angle, but I do think it served a real purpose.
It also laid a lot of groundwork for the nature of Hank and Marie's marriage. Marie became a very sympathetic character through Hank's convalescence when he was pretty much intolerable -- realistically so given his situation, but still. Her being presented as a harpy with her own set of problems earlier on kept her from being perceived as an angel throughout that storyline. Plus, she came back to those habits when she went on that lying real-estate binge, showing just another example of how people's morality can to to pot in stressful situations.
And Hank standing with her (he knew about the stealing, right?) says something about the strength of their marriage, which often seems so awful. I have a feeling this may come into play in the final season, Marie having to make some choices between her husband and her sister.