well yeh if you touch the earphone housing while its playing loud then you can feel the armatures vibrating inside ( however i actually think it might be the air being expelled from the ports on the low drivers that causes the housing to vibrate) if you put your hand over any ordinary port on a home or car sub you will find that the pressure inside the box forces air to be expelled very quickly, this improves the depth and response of the bass and has since been implemented in the se530, Q-jays, and others, this is an indication that the bass is big when the actual earphones starts vibrating, however the vibration can mean bad things for sound usually as it disturbs frequency waves, howver shure and jay's seem to have this covered because the bass is perfectly controlled.
however its not a great thing really as it can be uncomfortable, but then again you just turn the bass down if you dont like it dont ya. its nice to know if you want big bass it can be big enough to vibrate the earphones in your ears.
however the actual earphones dont cause the vibrations to be uncomfortable, its the tips! if you use the silicone tips then its just too much and you will pull them out to dig your ears! however i find if i use the foam its a much snugger fit and the vibration is only felt if you go wild with the sub control.