My guess is that they were losing a lot of money doing this. (Back story) I've had an on-going problem for about 2 years about slow speeds and contacted the BBB because nothing was being done after numerous complaints over the phone. They did a fix and the problem still continued. I've posted on DSLReports and my ISP's Social Media team helped me out so I continued to use them. I've received numerous credits to my account by just complaining to the SM team, which I think is more than fair--even though I didn't specifically ask for credits.
Nearly every time I tweet at a company they either don't reply, or ask that I call them instead.... WHY YOU DO YOU EVEN HAVE A TWITTER ACCOUNT?
It's only if you have 100+ followers, that companies are more likely to go out of the way to help, in my experience.
It's one of the few ways that new social media is actually providing value for me.
Some specific examples where I can recall using it: (1) Engaging the Microsoft developer team to fix up an issue with my account (2) Engaging Air Canada to ask about using my Aeroplan points (3) Engaging Commonwealth Bank to say thanks for great customer service and recommending someone I did deal with in person at a branch (to which they replied they would pass along the commendation).
All times I had a faster and more satisfactory engagement than if I had used phone, email, etc (as I'm reminded when I have to revert to these methods)...