I think the wildcard is great and I'm John Capel thinks so as well. Has this been around for a long time or is this a new thing added by iaaf and will the olmpics adopt it someday? No matter what an athlete has done in the time in between they should have the right to defend there title, I think so anyway!
The wild card started in 1997 in Athens. Its okay for worlds, but it would be terrible for the Olympics. The Olympics is big enough as it is, the World Championships could use the star power.
As I remember the wild card was partially created because of Michael Johnson, he was hurt around the time of US nationals but IAAF still wanted him to compete so they came up with the rule. I'm sure there were other factors too but I know that played a role, I'm in favor of it.