Does Sergej Karjakin proof that criterias for Candidates were high-handed?

If you just use ratings, there are ways to manipulate that.  Draws, ducking certain competitors, playing in weaker events, changing how active you are, etc.  Having some tournaments where the prize is entry to the candidates is a good idea.  Another idea is name some top tournaments for the year like maybe 4-8 events and then use an average performance rating (or combined score) for those events.  Personally I like the idea of a large tournament, but you break the field into matches.  For example the tournament could have 50 people, but then the top 16 go into a series of elimination matchs of maybe 5-7 games each.  That is a lot of chess but it would be hard to argue the results.

Maybe you're right. Anand and Carlsen don't want to show their tricks before the show...

Some people are consistent, others are not. Also, certain players are much more motivated when competing in official events (for example, Gelfand, Grischuk). They just can't do their best when only money/fame is at stake. Need real titles to be at stake.

I was thinking in Karpov's and Kasparov's tournaments. We can see his absolute dominance, no matter if it was for preparation or a higher prize tournament, they always shows their superiority.

Exactly how do you think somebody could manipulate their rating to 2780? None of your suggestions would allow a non super-GM player to get up to the 2780+ that would be required to be in the top 8.

You can't make yourself that high, but if you are there or close, you can consolidate for half a year or something along those lines.  People outside that range may have a harder time moving up if the higher rated players avoid them more often.  There needs to be incentive to keep winning.  Although it does take a lot to get there, if you give too much benefit to having rating points, the gap between the haves and have nots will get wider and harder to close.

You still haven't described any actual manipulation that would allow somebody who isn't a super-GM to get into the top 8 spots. The elite already play mostly just other elite. Carlsen hardly ever plays 2600 players, for example, unless it's a woman or there are some unusual circumstances. 

If there is any substance to your idea at all, please describe exactly how somebody would play differently in order to manipulate the ratings, and what you think the effect of that manipulation would be on their rating. 

I did not say someone who is not a super GM would get in.  I am saying that someone who is just outside the cut may play a weaker tournament to do better and get a couple points, or someone who is already in may stop playing so they don't risk points.  They may be quicker to take draws against each other in top events to protect their ratings.  A system that discourages competition in some situations is probably not the best for picking the world champion.

So on what basis is the wildcard player selected? Purely at FIDE's discretion? That would be open to abuse surely. Or do they have to justify the selection in some way?

It is the sponsor that pays for the event that picks the wild card. Both Kazan 2011 and London 2013 were paid for by the Azeris, and because of this they also got to pick the wild cards (Mamedyarov in Kazan and Radjabov in London).

Playing in weaker competitions wouldn't work to gain points. When you play much weaker players, you get little or no rating change when you win, and you get a huge rating drop when you lose every once in a while.

I think players are catching up with Carlsen and Anand styles. I don't think MC and VA play for wins. They are quite satisfied with draws, and only looking for opponent mistakes.

Still it takes a lot to play both of them. It likes the tournament is a warming up, while others strive to improve their ratings.

It likes tennis players warming up tournaments before entering Grand Slams.

Hindsight is 20/20. Radjabov had a terrible tournament; either Karjakin or Caruana would have done better.

Seems that Magnus took the hint and pressed the "Turbo-Boost"-button against Karjakin and Radjabov. 

Poor Radjabov - looks like 2013 won´t become a great year for him.