Some great posts so far. Weepingsam's remarks on light and Peter's on the motif of "stuff" both answer, in their own way, Glenn's central question: what is the relation between the corporate world and the sexual/violent noir world?
Let me start my answer by noting that Bad Influence is built around doppelganger obviousness. By obvious I don't mean that's how everyone reads it (though the comments to the latest post suggest many do), but that the film evacuates other interpretive possibilities. One thing I find interesting about dopperganger narratives is that the "evil" double never gets psychological depth. The same holds true for Bad Influence, even when the editing positions a series of point-of-view shots from Alex.
What's particularly striking - and why I call this obvious - is that unlike some other doppelganger narratives (Strangers on a Train, say) Alex hardly seems to have a psychology at all. "The cops won't believe this guy even exists." I don't believe he exists!
The thematic obviousness is in many ways a nod to noir, where Big Ideas got expressed in pulp form. However, neo-noir does not fully sum up this film. Certain moments of pastiche are there, particularly in the directional lighting, the slow tracks, and the costuming/makeup of the fiancee...
(remarkable how a Veronica Lake look comes across more as Color Me Beautiful...)
Rather than retro-noir, I'm inclined to say the film owes much to the film gris - films like Body and Soul or Force of Evil, which allegorized capitalism as criminal activity. That said, when pressed, it's hard for me to figure out what the film is saying exactly about business or what its target is. Office politics unfettered from morality? High finance? Consumerism? Credit economy? Is Michael the bad guy with his Sharper Image loft and credit card debt? Or Alex with his Armani suits and nightclub hookers-and-coke dissolution? I'm interested in possible interpretations film clubbers might have.
Finally, I should note that all this allegorization comes at the expense of women. There's a long-standing feminist critique of noir, particularly the femme fatale. But here the women are not even interesting characters, but rather pawns for the screenplay. And am I right to say a subsidiary theme is that carpe diem means men should not get involved seriously with women? In other contexts, that might be welcome libertinism, here it soured for me.