So you have an active twitter account and have thousands of fans on your facebook page. Why blog?
Simple. You are not in control of twitter or facebook or any other social site you may be using.
Social sites like twitter and facebook will help you build a community and connect with like minded companies and individuals, but say for arguments sake, that twitter or facebook was down for one reason or another. No more notes, no more tweeting and retweeting, no more quirky facebook updates, no more you tube. How else would your community access your information? How else would your community find out what great deals you have to offer them? Or what the details of your event are?
Twitter, you tube and facebook and other social sites are great for making initial contact, but you must have a hub, which will become the reference point for your business or for your event. You must have a channel through which to fully explain your strategies and engage with your community on a one on one basis and at length. Use your social sites to direct traffic to your blog. Tease your followers will little bits of information and then using links, shepherd them back to your website where you can have a more intimate discussion with them. Let your blog be where you finally get down to business.
A blog will give you an opportunity to sell yourself in your own words; to personalise your pitch and listen to your clients while giving them a focal point for any and all information relating to what you do.
Constant updates on your blog will make your company or event more accessible and even more credible. While social sites may give you awareness and attention, your blog will give you trust.
Above all else, you have an incredible amount of control of your blog since you own and control it!