According to the Huffington Post:
Kim Kardashian will go off Twitter and Facebook on Wednesday to support World AIDS Day and won't sign back on until $1 million is raised for Keep a Child Alive, Alicia Keys' charity. Alicia, Lady Gaga, Justin Timberlake and Usher have also made the pledge.
Here is Kim's ad, which reads: "Kim sacrificed her digital life to give real life to millions of others affected by HIV/AIDS in Africa and India. Visit BuyLife.org or text 'KIM' to '90999' to buy her life now."
So, donate to a good cause if you want Kim back on Twitter.