In my theology class today my professor talked about some of the issues facing the church (meaning the body of believers). In his opinion, the biggest obstacle in the 20th century was answering how God could allow such grievous suffering. With tragedies such as the Holocaust, and dictators such as Fidel Castro this was certainly not an easy question to answer.
He feels that now the biggest challenge to the church is the idea that there are many ways to get to heaven. Not only is this something held by several religions already but many Christians would even say that Jesus isn’t the only way. This could be called a form of universalism and it is very dangerous.