Well grenades pose a big dilemma. Without them, most team oriented games would devolve into epic-camp fests, where people would just find a defended spot and camp. Without grenades the camper would have a huge advantage over anyone playing offensively, so no one would play offensively.
So grenades are in games. Unfortunately in all to many games the grenades are too effective and easy to quickly throw out in large numbers (id est spam) so they piss people off as they are to difficult to avoid. CoD4 I feel tried to remedy this, only giving the player a single grenade as well as a grenade indicator on the HUD that warns you when you are close. Unfortunately someone at IW must have gotten high one day so they decided to make grenades be throwable without having to switch to them ("on the fly" throwing) unlike in other games when if you switch to grenades you're stuck if you're engaged in close quarters and they also allowed you to "cook off" grenades, letting the fuse run out so that the grenade will explode before anyone could get away from it, even with handy inficator.
IMO, the most balanced grenades where the BF2142 ones, firstly you had to pull them out like a separate weapon, second you only had two, third their radius was not as big as grenades in most games, and finally (and most importantly) there was a visual indicator (in the form of a smoke trail) and audible (in the form of a sizzling sound) that they were around. The only bad thing with them was that if there were multiple ammo boxes near by they could be restocked faster than they were thrown, and you threw them a little to fast. But even so, they were pretty easy to dodge.
So yeah, grenades need to stay, they just need to be implemented a bit smarter.
