Businesses are increasingly using social media networks for communication and advertising. So it makes much sense for businesses to integrate social media marketing into their normal advertising scheme.
The social media marketing reality is not only entering areas such as email marketing but also PR, CRM, etc.
Many ESPs and CRM vendors have already included social media marketing integration. Many SaaS CRM systems, for instance, enable you to see the Twitter updates, Facebook updates, LinkedIn updates, etc. of your customers.