The disparity between Borislav Ivanov's good tournaments and bad tournaments seems too great to me. With the advent of such strong computer programs, cheating has become much more of a problem. These days a computer running on an iPhone could beat most grandmasters.
However, I don't believe that cheating is a problem in the elite events. Professional players have too much to lose to attempt to cheat, and besides, in general, they would be horrified by the thought. There was a scandal a few years ago during a World Championship match known as "Toiletgate" [when a 2006 World Chess Championship match between Vladimir Kramnik and Veselin Topalov nearly collapsed with Topalov's manager complaining that Kramnik was using the toilet too often during each game – implying that Kramnik might be receiving computer assistance], but I think this was just an attempted psychological attack by the manager of one of the players.
Players who have generally been found to be cheating have normally been playing for one big payoff – a big first prize in an amateur event or playing towards an international title to become an international master or grandmaster. The problem is with the risk/reward ratio. A player found cheating might be banned from playing for a year or two, but if they're discreet it's very difficult to prove. The Fédération internationale des échecs needs to be stricter on players who have been found cheating.
Currently we have an odd situation whereby if your phone makes a sound during an internationally rated game then you are forfeited and lose the game. However, this does not stop players from having their phone on silent, or off, and then going to the bathroom and checking the position with the computer (as is alleged to have happened this year in the German league the Bundesliga). As far as I'm aware, no one has ever used a computer program to cheat against me, but when I was very little someone did take a move back.
Gawain Jones is a chess grandmaster and 2012's British chess champion