It's no problem for the foam to loose the hot break, since that's made up of denatured (coagulated) proteins. Once the proteins have denatured they don't contribute to the head of the beer - they're insoluble and just fall out and sit at the bottom of the fermentor or keg. (This is covered in the podcast - Jon mentions not boiling the wort too hard to avoid denaturing many of the proteins.)
Depending upon how much beer/hops you loose, you could have these problems:
- undershooting OG to hit expected post-boil volume, or
- hitting OG but with smaller post-boil volume
- reduced IBUs, both from the possible loss of hops, but also decreased efficiency with a smaller volume of wort
But I think you'd have to have one serious boilover for it to make any noticable difference.