I hate Comcast (Nasdaq: CMCSA).

They never show up when they say they will. They tack on service charges without notification. And their customer service people are cold and unhelpful, spending every second avoiding questions and attempting to sell unwanted add-ons.

Last month, I had to reschedule the reinstall at my new apartment four times. The first time I installed Comcast (before I moved), they held me hostage in my home for nine hours, kept transferring me to different departments, lied about showing up, and then tried to blame me for their technician getting lost!

I'm not alone in my loathing. My Fool colleague Rick Munarriz has written multiple articles detailing his hatred for Comcast:

Other disgruntled customers have started blogs such as ComcastMustDie.com. Mona "The Hammer" Shaw, a fellow Virginian, went so far as to wield a hammer to her local Comcast office after an unpleasant experience in 2007, as this Washington Post story details. In 2008, according to dlsreports.com, Comcast reached an all-time low in customer satisfaction, getting a measly 54 out of 100.

So who cares?
I'm aware that this rant is consumer-focused, and that The Motley Fool is investor-focused.

But remember, companies that treat their customers poorly will eventually fall. A couple of years back, Vanderbilt University Professor Bruce Cooil found that as a company's American Customer Service Index (ACSI) rating improved, so did its the stock price. Cooil also showed that companies with lower ACSI ratings posted declining values over time.

The logic is simple: Companies (like Comcast) that give customers a reason to leave will eventually lose them. Right now, disgruntled customers come back to Comcast because there are few other options. That's my own predicament. But new companies emerge every day, and once a better option comes along and takes over some of the areas where Comcast dominates, the cable monolith will inevitably suffer.

It's a vulnerable time …
Comcast is in the process of fending off threats from a new crop of competition, too. Tech blogs have swarmed over the story of how Comcast is considering blocking Netflix (Nasdaq: NFLX) streaming, and how it's demanding a large fee from Netflix's streaming service provider, Level 3 Communications (Nasdaq: LVLT). At best, the new net neutrality rules provide a murky picture on how this will play out.

The companies could work out a deal, but I, for one, think this move is dangerous for Comcast. I think consumers are more likely to change cable providers than give up the luxury of being able to stream their favorite TV shows and movies whenever they want. Who needs a fancy cable package when you can stream everything to your laptop, PlayStation, or Wii?

Take note
At this point, Comcast may well be happy to lose me as a customer; I've spent hours on their phone lines and live chat modules. The larger point here, though, is what Prof. Cooil's study showed: Happy customers often lead to happy shareholders.

Whole Foods founder John Mackey said it eloquently:

The best way to satisfy customers best is to organize the entire business around satisfying the customer. Every communication the business makes towards its customers, its employees, and the media should be about putting the customer first. Ultimately the best way to satisfy customers' needs best is to actually put those needs first.

To be fair to Comcast, its credo -- plainly stated on its corporate website -- heavily emphasizes the customer experience. In my own experience, though, Comcast is not creating a quality product. Instead, it's leaving customers like me disgruntled -- or even enraged.

Do you think the time will come when Comcast will also leave investors unhappy? Sound off in the comments section below.

Anne Henry does not own shares of any company mentioned. Netflix and Whole Foods are Motley Fool Stock Advisor recommendations. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.