When you're looking at games like Monopoly or Chutes and Ladders, you're looking for fairness and equality. Everyone is at the mercy of the dice, and you should take the dice you roll (and the probability of something happening) into account when you roll them.
Taking Monopoly, for instance, you have spaces that are your usual spaces (which are your property tiles). When making a game with that in mind, and the fact that you want something to happen every now and then, you should space things out so the chance that someone will land on an action space is even enough. A roll of a 1d6 (one six sided die) is going to be much more different then 2d6. In fact, a 2d6 is going to be even more wildly different then a 1d12, since a 1d12 is all consistent (given the die isn't weighted) while 2d6 will produce more 7's than anything.
You have to also weigh in on if you want both negative and positive effects, only negative effects, how bad those are, ect... This all plays into how 'randomly' your spaces are hit. And, again, I will stress that the players have to be treated fairly in this regard. Since they cannot choose a path or how many spaces they move, you remove the tactical and strategic thinking from that aspect of the game. If it's something simple, like a child's game, then this makes sense. If it's more of an advanced game, you need to bake some tactics or decision making into the event spaces.