Some people and businesses are using Twitter very successfully, but many find it too fragmented. You are only allowed 140 characters which includes letters, punctuation and spaces. It seems that many are losing interest in Twitter as an effective social media platform.
Some businesses are using it very well for B2B (Business to Business) marketing and less for B2C (Business to Customer) marketing.
Remember that a tweet only has a life span of 6 minutes – it has a sense of immediacy. It does have a wide reach, but not as wide as Facebook, where a post has a 2-3 hour lifespan.