For the record, for anyone eavesdropping, Doug and I talked this out and he has huge ear canals. He has to use the biggest of the three earplug pieces included with the headphones, and they don't fit super-snugly.

For me, with the medium earplugs, they stay in quite securely and don't fall out unless given a rather serious yank. If the same yank had been applied to a standard pair of headphones, they would have come off my head, too.