I've heard enough people say the same thing to assume it must be true. I also saw a lot of this type of complaining (usually expressed in hyperbolic, super-outraged language) when I used to use Twitter.
This seems very counter intuitive though. Why would a company want to encourage people to make complaints in the most public way possible? It makes the company look bad, and encourages opportunistic complaining (I'm sure there are people who feign outrage over some small issue in the hope of being sent some coupons or a discount code).
Surely they'd be better off investing in private complaints channels (email, chat etc), and making it clear that you'll get the fastest response by using those.
I wonder if it's because the customer service channels were often outsourced or off-shored years ago, and are hidden behind layers of process and management. Whereas the head of marketing has the company Twitter account on her phone.