A new software has been developed to expose how many of a Twitter account's followers are real people and how many are basically shells and spambots. A prominent UK politician was shown to have 40,000 fakes, but that's peanuts—only 29% of Lady Gaga's overwhelming 28-29 million followers are real. (Still, that would mean she has over 8 million real followers, more than most.)
I'd love to test this out on an old rival of mine from my former days as a teen editor, and I'd love to hear what percent of other major accounts (Justin Bieber, etc.) are valid. Then, once we get the kinks worked out, we need to get Madonna on Twitter. Cher is a hard act to follow in that medium, but still!