I believe PEDs gate to gate will come to EZY in a few weeks time for all periods except during low visibility approaches.
Electronic devices may be used on easyJet on the ground currently when the door is open
In terms of the gate staff I have seen them ask people to stop their phone conversation whilst walking to the aircraft and that was on a UK domestic flight by non-easyJet employees. I don't think they would enforce this on just EZY pax.
As for Facebook it'll come down to cost I should imagine. In fairness to them they do allow you to post direct messages and post to their wall if you have a query and you get a quick response normally. A few airlines allow neither.
Edit: ok, I've found a reference (it's a dated manual but I assume it's still current). I can't post what it says however it's all in the semantics. Instead of the crew saying "prohibited" I think "restricted" would be more appropriate. I hope that makes sense! :-)
Additionally although fuel is loaded on he STBD side I know that the airbus classes the port wing (and an area defined around the wing by a few metres) as part of the "refuelling" zone. As EZY could potentially be boarding or disembarking during refuelling I'd imagine they and and the fuelling agent do not want mobile phones used as there is a potential for a fire hazard. I know for fact refuelling trucks have a No Phones sign on them so they must be perceived as a fire risk, otherwise why would they have the sign on the trucks?
Also see the following guidance from Airbus. See page 5. It states mobile phones be turned off as a precaution when refuelling with passengers onboard.
http://www.airbus.com/fileadmin/medi...HAND-SEQ01.pdf