A marketing firm down the street was in our office a month ago. They have a new beverage (non-wine) that is quite remarkable and for the last six months or so they have been marketing this product in the nutrition market space. The brand currently has a beautiful site, built primarily in flash, with some great photography and limited product information.
Before the meeting started, I did some quick research and noticed that this brand was being talked about in a lot of different forums. In fact I found at least 20 forums where this product was mentioned. Some of the comments were very positive, some were inquisitive, and there were some negative comments also (most of the negative comments were around the product not being found in local stores, or a rebate for a coupon not being received yet).
Unfortunately, the brand manager (who has been doing a great job getting the product into the retail market) had no idea that their brand was being talked about.
In this modern era, we are seeing more and more transparency in brands. It's not uncommon for a brand to have a blog and allowing customer comments. We are seeing brands have twitter accounts. Brands are opening up their websites for customer comments, reviews, etc.
The bottom line is: if you have a remarkable product, an average product, or a poor product, people are talking about you. If you don't allow user generated comments on your website, it won't stop the conversation.
This conversation can happen right on your website, where you can quite easily participate in the conversation (and this is the best place to have a conversation about your brand). This conversation will probably happen on other websites, where you can use monitoring tools, and probably participate in the conversation also.