The “Oprah Effect” on Twitter was fairly significant after the daytime talk show host sent her first tweet. Twitter saw a 43% increase in traffic due to the Oprah Effect because her legions of fans quickly took to the social networking site to follow Ms. O.

Market tracker Hitwise shows the Oprah Effect on Twitter in the graph above – you can see the traffic bump up once Oprah signed on to Twitter on April 17.

This shouldn’t come as much of a surprise, considering Oprah’s ability to land books on the bestseller’s list by featuring them on her show.

While Twitter traffic saw a bump, the “Oprah Effect” on Twitter showed that 37% of visits to Twitter.com that day were new visitors – plenty of new Oprah followers, no doubt.