As of this week, Twitter is doubling its character limit to 280 characters for nearly all users. The rationale: New users might find it easier to start tweeting and might stick around. Japanese, Korean and Chinese-language tweets will keep the original 140. As Twitter explained it, these are denser languages, requiring fewer characters to express what might take much longer in English, French and Spanish. But will it get more people using the service? We ask Michael Pachter, managing director of equity research for Wedbush Securities.