When money is involved - usually through betting - then corruption may well follow. VAR is just another avenue for ii: it's not as if there haven't already been dodgy World Cup events/decisions before.
My guess is that VARs will lead to an increase in the number of penalties awarded. Incidents, when slowed down, often look like they could have been penalties because it will appear that there might have been some kind of contact. To be sure it isn't a penalty there would need to clearly be no...