And, given the traditional designation of caring work as female, it is no accident that Samantha, the OS voice, is chosen to be female. Just as Theodore saves people time by writing their letters to loved ones, he finds intimacy with 'Her' in record speed and no work required. The OS reflects his own desires and flatters him in a way that a conventional wife is supposed to. Wives were once the possession of their husbands, and now we have Samantha, initially with no agency of her own, a purchased possession. In the words of the advertisement, the OS 'listens to you and understands you and knows you'. It/she does as Theodore pleases, including having sex, a conventional dream of woman as object.
On one reading, the film is undoubtedly sexist and it is hard, especially given the prevalence of pornography on the web, to imagine the gender roles reversed, with a female lead falling for a male OS voice. However, Spike Jonze complicates matters by giving Theodore's friend Amy a female OS friend. It is a platonic relationship, which matters for the credibility of this clever movie, and this still allows us to avoid the realization that intimacy cannot be delivered on a plate so to speak. But the hilarious twist in the film is that these individually designed and tailored OS's, that develop uniquely in response to Theodore or Amy's instructions, presenting themselves as in a special relationship, turn out to be simultaneously 'in love' with and servicing hundreds of others!