My two cents: there are companies providing social media CRM services that provide real time
1. market sentiment on their customers opinions
2. alert when complaining tweets require client service to follow up.
The monitored tweet volume is very small as the key words are mostly limited to company names or key products. Especially most complain directly @company handle.
Most of this can be done manually, to take my previous CPG client as an example, people from each merchandise group manually check the amazon review on the product skew they run and work with customer service together to follow up on bad reviews. They try really hard to collect online feedback to understand what people like and not like about the products.