Veteran Bollywood actor Amitabh Bachchan has crossed 18 million followers on social networking site Facebook. Thanking his fans on the networking site, Amitabh posted, "18 MILLION !!! Followers crossed ! Thank you so much my FbxTF .. my Facebook extended family". The 72-year-old, who has been in the industry for over 40 years, has just completed shooting of "Piku" movie.