According to a PowerPoint presentation by Mary Madden at Pew Internet, their survey showed that in 2011 about 74% of adults are now online. Their survey also showed that only about 13% of the surveyed online users use Twitter!
These findings suggest that for most downtown merchants, Twitter offers limited ability to reach shoppers in their local trade areas.
However, the table below from Pew shows that those in the 18 to 34 year old range are much more likely to be Twitter users — 18% or 19%– than those over the age of 45 (no higher than 9%). Downtown merchants with a local geographic market area and a younger customer base will probably be more interested in experimenting with Twitter. The ease and low cost of using Twitter also argues for such experimentation by them. For those able to offer merchandise to a large regional or national market, Twitter will probably be even more effective.