By strict Kevin Bacon rules there's some double counting there. Someone being in a band with someone should just be one link, the same as being in a film with them. Instead he breaks it down into two jumps, 1 for the first person to be linked to the band, then for the band to be linked to the second person.
Just a nitpick, not meant to detract from the geeky awesomness of the project.
In now looks like Interpol is no more than 15 steps to all of these bands. They must have just updated their data or algorithms.