Which social media platforms seem geared towards personal use and which ones seem to work better for business?

I would say that the following seem to work better for business:
YouTube/Video - business can create brief product demonstrations or instructions.
RSS/Email: helpful for businesses who have a client email list to announce new products or special events such as workshops; 


The following seemed geared more towards personal use:
Blogs - Feedback on personal opinions or statements can be helpful to an individual soliciting advice or product reviews.  If used on a business website, I would think someone in the business would need to be assigned to monitor the direction of the blog - i.e., if one customer has a bad experience, misconceptions, inaccurate information would need to be addressed immediately before it spirals out of control.