Online, reputation is everything. It drives you professionally, personally and algorithmically. Have a good one and you'll see positive returns. Develop a bad one and you'll have to work doubly hard to come back into your customers good graces.
While it's impossible to monitor every venue showcasing public opinion and reviews, you can work to protect your reputation by registering your known brand/name with as many social media, forums, and discussion sites as you can, especially the popular ones in your niche.
Why? Well anyone can register any name at a social media site and pass themselves off as you. Or just register the same name and tie it up so you can't. If you've worked hard at promoting your name (or a forum nick-name), people will assume it's you they see on various social media sites. Imagine their confusion when some interloper starts posting differing opinions or ridiculous comments! By not registering your name you've lost the opportunity to build on it and promote yourself in that location.
You've heard the old saying..."online, no one knows you're a dog"? It's very true. Anyone can come along and register your username, no verification or identification required. Once they become "you", they can seriously damage your reputation by making outlandish accusations or promises on behalf of your company. At the very least they unintentionally cause confusion. It could go on for a while before you find out about it and by then... negative opinions are formed, reputations are damaged and people are left scratching their heads.
If you think it's a big waste of time to go around and establish your branded username, consider the time and expense it will take to get those negative comments deleted and the confusion straightened out.
Also consider the added link bonus you'll get by taking possession of your username; many of the social media sites allow clean links in their profiles. (LOL - what kind of link builder would I be not to find the link opportunity in this! ;)
Be pro-active and register your brand/name on as many social media sites as you can. Tie up your username and avoid damaging your reputation, don't make it easy for anyone to steal your online identity.