@Zello: Sure, maybe, however for many monsters, by the time you see it, you are technically in a fight. Ever try to dodge a charging bear? Once you see it, you *are* in a battle.
But, I also think a really fast running monster tends to annoy people as much as random battles. Personally, if I have visual battlers, but the game forces me to run into all these really fast running monsters, it feels like it defeats the purpose, as the battles are unavoidable. Same thing if they always block the path.
Personally, I like the Bravely Default approach, or ksjp17's approach. Let the player decide. No one approach is going to please all players.
At least with visible enemies you have visual warning.
Another way of accomplishing this is with a random encounter gauge. But a reason why this still sucks is because it breaks immersion. The monsters are still coming out of thin air.
In an RPG you have an overhead view of the area, including behind the player. How is the player supposed to be really surprised at this point? That's asking a bit too much.
We should also mind the fact that, as I pointed out earlier, something is not surprising if it happens too often. People are used to defaulting to random encounters so they assume that all encounter systems need to recreate the surprise element. But if anything it becomes more surprising when you enter an area and find there are no encounters. (such as boss rooms) The fact this happens just goes to show a problem with the surprise excuse, since it's not really surprising that enemies are suddenly attacking you, but instead it is a mundane occurrence. The surprise is when it finally stops.
Also, if you are entering a bear-infested forest, it's not exactly surprising to see a bear now is it??
And maybe you'd see that bear coming in advance? You probably have SOME time to react. That bear is a visible enemy.
Granted, it may be impossible to safely proceed while that bear is still tailing you. Solution: Use a global switch, lock all exits until the bear is defeated. That's your random encounter.
Yes, it's annoying for things to happen suddenly. Personally I think the no-no is grabbing the controls away from the player. That's why I try to resist the temptation to have trip-wire encounters and events. Such a method creates a span of time before the event starts and the actual encounter, which is a good thing. It also means it's a depletable encounter (you have to fight it only once) which is another good thing. But the loss of control over your character happens instantaneously, which is a bad thing. But if anything this just goes to show how bad random encounters really are, because it's a laundry list of things a game shouldn't do conveniently wrapped into one.