Twitter's CEO making big product changes, but users not wowed

By Yasmeen Abutaleb SAN FRANCISCO (Reuters) - Since returning to Twitter Inc in July, Chief Executive, Jack Dorsey has made a handful of dramatic changes to the micro-blogging service - and promised more. Analysts say Twitter's stock price, which has reached record lows, is unlikely to rise until the company shows significant user growth. In a letter to shareholders released Wednesday, when Twitter reported its fourth-quarter earnings, Dorsey outlined for the first time his strategy for the comp