Garry Neville's analysis of diving:
http://www.dailymotion.com/video/xq65vw_gary-neville-tells-it-like-it-is-on-diving_sport
I don't like Neville, but you have to respect his analysis of the game. Whatever your stance on the issues he discusses, it is a much more difficult balancing act than most people acknowledge.
In my view, discouraging players from going to ground with the threat of a retrospective ban is going to result in broken legs. I know Bale has hurdled a few legbreakers this season and then been accused of diving (for example, at Liverpool away).
I like Neville as a pundit, and I think he makes some fair points here.
BUT/ there is no doubt that some dives are 100% clear and indefensible, and these should be punished retrospectively. E.G. Drogba holding his face against Napoli. Just because there are some grey areas, doesn't mean there aren't any black and white ones. The Gerrard one was a blatant dive too, no contact whatsoever.
Also his argument against retrospective action seemed rather confused, when he showed the clips of people getting booked unfairly for diving. The point is that referees wouldn't have to book players for diving if punishments were given retrospectively instead.
Generally I think you can differentiate between:
a) Players going down with no contact whatsoever (dive)
b) Players holding their face to get someone sent off, when there was actually no contact with their face or the contact is vastly overexaggerated (dive)
c) Attacking players actually creating the contact themselves, either through collapsing legs ala Lampard or throwing their leg into the defender ala Young (dive) [the most grey areas here]
d) Attacking players getting contact and choosing to go down to ensure a free-kick or penalty (ala Samba or what the Swansea player could have done) (not dive) [a little bit of grey here, but generally it's pretty obvious if there was enough contact to be a foul ... Young against QPR was a clear dive and should be punishable]