Users blamed Oprah’s popularity for causing the site to slow down when she issued her first tweet. Estimates are that perhaps over a million new users joined the site after Oprah discussed it on her talk show. A million users is nothing more than a guess and a very rough one at that. The estimate is based on a Twitter ID pre-Oprah and one post-Oprah. When compared there is about a difference of 1.2 million, which logically would mean 1.2 million people joined the site during that time period. The problem though is  Twitter no longer sequentially assigns user IDs so it really is a guessing game when it comes to how much user growth Twitter experienced during that time period.