There are 2 sides of the coin - consumer side (doesnt affect ME buying a knife), and a company side (company/brand image, openness, friendliness etc).
And owners\designers actually reading those forums shows a certain level of involvement.. Listening to your actual active client base is kinda important. Again its not necessary wasting time on forum chat.
The Giant Mouse product launches on instagram are a perfect example how it should be done, imho.
Web presence can be a good or bad thing. One company I won't name had a marketing guy who was a thin skinned abrasive sort. He ticked off many here. Not enough for me to boycott the company but enough to sway buying decisions that were close.