You’ve heard about the Oprah effect on books featured in her book club, or on Barack Obama’s election. But what has her effect been on Twitter (she started tweeting on 4/17)? Hitwise reported that Twitter’s US share of visits increased 24% on the day of her first tweet (graph below).

Additionally, Ryan Block, former editor-in-chief of Engadget reported that 1.2 million new accounts have been created since Oprah’s mention on her show. If that’s true, that’s a 10% increase in Twitter users in less than a week. She already has over 600,000 followers.

I have no idea how this significant increase in users will actually effect the Twitter community, but it’s sure to make an impact one way or another. Also, here’s another example of Twitter’s mainstream growth: in the 10 days since Ashton Kutcher (@aplusk) broke 1 million followers, he now has an additional 400,000.