Is it Really Effective to Comment on Blogs and Websites??

I'm still learning and navigating my way around this whole internet thing. And I was just thinking the other day "Does it really matter or make a difference to add your comments to blogs, websites and groups?? Is that really how you get to know people, or get the word out about your business, shop, etc.? Are there some key things to say... do... or comment about?? Do people really get to know you this way? Has it helped with your business or sales? I'm really not sure. If you have some thoughts or comments on this matter or if you have some experiences to share. Please feel free to comment on this blog (Curby's Closet). Let's share an learn from each other. Okey Dokey?? Who knows it could be Cool!!