Andrew Gabriel wrote:

With ES lampholders, the main risk is gripping a bulb
to insert/remove it, and being electrocuted by exposed
metal of the lamp base. In most countries where it's
used, it's not possible to guarantee the live connection
is the tip, as live/neutral polarity isn't preserved into
appliances. (In the UK, it is required that the tip is
the live connection of an ES lampholder.)

But all the recent ES lampholders I've seen are designed so that the
threaded part of the cap doesn't make contact until the lamp is screwed
almost fully home and the skirt extends just beyond the cap making it quite
difficult to touch a live cap. Illustrated fitting instructions (e.g. Ikea)
tend to be a bit vague but often seem to imply that live should be
connected to the outer contact and neutral to the central pin.

With this arrangement the live contact in an empty lampholder is less easy
to touch with your fingers than the contacts of a BC lampholder.

--
Mike Clarke