I think, especially considering the level of threat to Bush in that country, that:
1. Bush's security team were at least lacking!
2. The 'thrower' was lucky not to lose his life to a gun shot from the security team. They wouldn't be thinking 'oh its only a shoe, that's ok'. They will obviously take ANY threat to a President VERY seriously. However, point 1 may have a bearing on that.
There seems to be a problem with the link in the op. See the incident here: