Twitter has revealed its top hashtags for the year. The top hashtag this year was #egypt, following the downfall of president Hosni Mubarak in February. Other popular trending topics included the Arab Spring and the Japanese earthquake.

Naysayers still dismiss Twitter as a platform for people who post self-promotional links or trivial details about their daily lives -- this tuna sandwich is tasty! --- but there's no denying its growth.As we reach the halfway point of 2011, users of the microblogging service now post 200 million tweets a day, Twitter announced in a blog post Thursday.