IDENT
 

"Dudes" trying to be cool. Morons.

It's incorrect. Next time ask them how ATC know who's identing.
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An IDENT squawk can only be used by a controller to identify an aircraft when it is observed as a response to the controller's request for IDENT so anyone (not just FOs) who presses the button without specifically being told to is wasting both their own time and the controllers.
NB There was a time in the early days of code/callsign conversion when an IDENT was required to tell the computer to convert the code to the casllsign but these days have long gone.

I want to said "never push IDENT" if the ATCO doesn't ask you to do it.
Suppose in the same area, a controller ask to an other aircraft to push IDENT, and you push IDENT, it can be a source of misunderstanding, and the ATCO can think the airplane he ask to push IDENT is the wrong location on his screen.
It can become very dangerous...

Acceptable to simply IDENT when requested without verbal acknowledgement, or not?

Not acceptable in the UK - see CAP413 Chapter 5 Radar Phraseology :

5.9 The pilot must respond to SSR instructions, reading back specific settings.
"BIGJET 347, squawk ident "
"Squawk ident, BIGJET 347"

As fredix says above, if the wrong aircraft squawks, all sorts of issues can arise.

Not clever at all. Annoying AND unacceptable. Downright stupid.

Reference
 

It is mentioned in FLIGHT PROCEDURES (DOC 8168) - SECONDARY SURVEILLANCE RADAR (SSR) TRANSPONDER OPERATING PROCEDURES

1 OPERATION OF TRANSPONDERS
1.1 GENERAL
.
.
1.1.6 Pilots shall not SQUAWK IDENT unless requested by ATC.


Hope this helps.

As an ATCO this is a conversation that we've been having over the last week or so. It's definitely on the increase. I just ask them to Squawk ident and often the reply comes back 'squawk ident again'.

In 18 years of flying, I've never once been asked to Squawk Ident.

You could say that, yes...

Have never seen it requested at my home unit either. A bit quieter out here you see.

Different units have different procedures, however it is typically used at busier units where there is a lot of traffic on the Radar. Have also heard of it being used en-route for similar reasons.

A controller can identify a departing aircraft via a known airborne time as an alternative to an ident squawk but this must be done within a fixed distance from the end of the runway so at busier units it may not be possible to use this method.
Used to be done using an 'on channel' intercom (ie the tower controller selects the frequency of the departure controller and tells them of the departure without transmitting it on RTF) but nowadays this procedure seems to have been phased out in favour of making a telephone call or the tower controller just transferring the aircraft to departures and the departure controller requesting the ident..

Busdriver01. Maybe at some airfields, but not the busy ones, unless things have changes!

Just out of interest: its almost exclusively used in the UK - is the UKs radar environment so much different from the others ? Never had to squawk ident out of Amsterdam or Frankfurt or other real busy airports. Or is it just one of these things that always had been done ? Should not Mode S give you all the required info ?

I appreciate what the rules are regarding the use of the squawk ident feature however, as an en route controller on a high workload congested r/t sector, it does actually help when the pilots are patient and if they have not been able to check in for some time, a few pilots hit the ident button as an unwritten rule that they are listening and waiting. It is appreciated as calling on will just either block my readback (which is necessary) or block another pilot also trying to check on. With traffic increasing, I have noticed the r/t discipline of more foreign low cost crews think they are the only ones in the sky and I am afraid they are not.
Anyway, nothing to do with the departure aspect however I can answer that the reason for the request to ident is to do with the correlating the flight plan with the radar track and hence it is identified. For this reason, you should not be asked to change ssr with ident as the lag in the system could actually correlate the flight with another flight plan and we would get the wrong callsign and destination among other things incorrect with radar track.
Hope this helps.

It doesn't bother me at all but I'm used to make fool of them asking if there is any particular reason for squawking ident.
I do usually suggest to call maintenance on arrival to fix their transponder :)

It is not necessary to correlate the Mode S address only the aircraft identification feature (callsign input into FMS) with the FPL callsign on the FPS. From my experience it is only NATS units that use the ident feature to identify a/c on departure.

Is it the case that the callsign displayed on NATS systems is derived from mode A by callsign conversion rather than displaying the mode S flight ID? Maybe this is why the ident is needed?

NATS units do not currently show Mode S correlations, all code/callsign conversions come from Mode A.