When an RP that is going strong begins to die off... who is the one to blame?

Now this can vary from roleplay to roleplay, but in my understanding the only time a GM is ever at fault is:
A: They failed to create an interesting world environment (mostly from the get go)
B: They ditch the RP
C: They let problematic participants continue to play

Other than that I'm willing to bet that most roleplays that die off are due to the players.

[u][b]Case 1[/b][/u]
A large group of players are in a roleplay and one player in particular is a bit too eager to post. As soon as they see an opening they pounce their character into the situation and reply, even if they replied a couple of posts earlier and even if it has the risk of character/scene breaking.
[b]Problem:[/b] What this does is kill the flow. This player probably doesn't realise that they have blocked out several others and because of that it becomes immersion breaking. Other players will only take so much of this before they throw in the fowl and say that they're done. At that point you've got a roleplay that is at risk of dying all because of one obsessed individual. 

[b][u]Case 2[/u][/b]
A roleplay starts and after several posts in IC, 1 or 2 players decide that they want to drop out. One of them announces publicly, the other just leaves silently.
[b]Problem:[/b] While this is acceptable as things happen, there are ways to go about this and ways NOT to go about this, especially when the GM has spent time setting up a story and a role for each character. You, as a player, chose to enter the roleplay so therefor it's your responsibility that if you bow out you at least tell everyone and talk to the GM about how your departure is going to affect the roleplay. And if you're the type of person that leaves silently while the RP is still running strong, then thank-you for being the jerk that you are, because by the time everyone realised, what could have been a clean departure could now be a mess because people were waiting for your reply.

[b][u]Case 3[/u][/b]
Metagaming
[b]Problem:[/b] Not even going to gloss over with an example, but this has to be the one thing that will annoy any roleplayer. I've seen characters gather information from invisible sources, I've seen characters make impossible dodges from non-telegraphed attacks, and even use information from the OOC that hasn't been implemented in the roleplay yet. The problem is things like metagaming is that it really is a virus. Once it is allowed in an RP it will spread and people will accept it as the norm because everyone will believe it as Canon.

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Do why am I bringing these few case studies up on various RPs I've seen or participated in (and I have plenty more)?

Because I heard of someone tell off a GM for making a boring and dull roleplay.I'd like to dispute this fact with several key pieces of evidence. Firstly, this roleplay was running pretty strongly and we have a group of people that are thoroughly enjoying it. We just happened to have a couple of non worthy people that were terrible players or ditched the RP. Secondly, looking back at this persons posts they seemed to enjoy it otherwise they wouldn't have collaborated and written up detailed posts themselves. Finally, the original OOC was quite clear of the expectations of the Roleplay. If you failed to grasp that then it is not the GMs fault.

So yeah... I'm annoyed and having a Mega bitch for once because how many fucken roleplays do I have to enter where it is the individuals, who have entered with me, who are the ones that ruin a perfectly good roleplay.