In anything that is cloud based there is going to be some level where some hacker could get in and destroy everything. Most people on this site use cloud hosted servers, all of which would be at risk if Amazon or Rackspace got hacked. BI in the cloud is a new space and will be cautiously entered by some, but benefits will outweigh the potential risks and just as has happened in every other segment of cloud computing.
(will write more soon)