Many if not most major brands have a social media presence now, including a Twitter handle. Some brands, especially ones with a service orientation (such as airlines or major retailers), are able to use Twitter to forge connections with customers and facilitate better responses in times of trouble (ahem, flight delays and lost baggage). When a corporate Twitter account interacts with users, it fosters a sense of relatedness that motivates ongoing customer engagement.
Watching brands interact with each other can also create a feeling of relatedness. It gives brands a personality, and because the interactions feel unplanned (and perhaps also because it’s hard to believe rival brands would coordinate a social media interaction), users feel like they’re peeping in one something real.
Chances are, these sorts of brand tweets originate from playful social media managers more than a deliberate brand strategy. Nonetheless, they are an effective and fun way to engage users by helping them feel a relationship to the brand.