In order to get top dollar as a seller, you have to do a number of things: stage your home, be marketed where buyers are looking, and be priced to the mass market of buyers. However, sellers might ask their agent if they are utilizing social media such as blogs, Twitter, Facebook, etc. for one very important reason: it can help to identify unique buyers, and unique buyers will often pay more! Leading marketing guru Seth Godin had a recent post about the power of Twitter you might want to review.
What is a unique buyer? A unique buyer is someone who may desire a particular property for more than its utility of say "four bedrooms, three baths, three car garage," etc. An example of a motivation of a unique buyer might be that the property is in close proximity to a relative or a friend of theirs. Another might be the social status a given neighborhood may have, or who may have owned the property before. Uniqueness about the property itself can drive higher offers, for instance, it may have a separate entrance for a home based office or mother-in-law suite.
Finally, unique buyers want to be in the know, ahead of everyone else. If your agent understands this, and can communicate that outside of the traditional MLS posting, it can drive unique buyers to your property and result in a faster sale for more dollars!