Hi, i have my iphone plugged into the usb port of my laptop charging and when i run my hand over all the metal parts from the frame to the back it makes a weird vibrating sensation, as if there is too much electric current running through it or something. My gf's macbook pro does this too sometimes when you run your finger along the metal near the touch pad. Is this normal or is it something i should be worried about? what is it? thanks...

i've felt it too, no idea man.

It means your power adaptor is not grounded (linked to the 3rd pole called earth).

Only "Live" and "Neutral" are linked

What you feel is a little electric potential difference.

If you unplug the power it will disappear.

It's ground leakage. Ground the laptop, or the charging device, and the buzz will go away.

It's normal, albeit annoying, and sometimes 'prickling-ly' painful.