During the laning phase, keeping track of where your laning opponent(s) is located is quite important. Are they hiding in the bushes waiting to jump out at you? Did they go back to buy? Are they headed to the jungle or to another lane for a gank? As important as keeping track of your own lane is, you also need to keep track of ALL enemies, not just the ones in your lane. You can help your teammates and they can help you with wards and calling “MIA” when their laning opponent disappears. But you should not always rely on these measures alone.
Whenever someone gets ganked, dies, and then starts bitching because I didn’t call MIA, I tell them the same thing every time; “Use your mini-map.” Watching the mini-map is the easiest way to know where your enemies are. If you can’t see an enemy (or they have a global ult) they are a threat to your lane, and you should be playing more cautious. Do not rely on your teammates to tell you when someone disappears from their lane, because they can’t always let you know. I cannot count the number of times where I have been 2v1 and one of them breaks off while I am still engaged with the other. I WILL NOT stop what I am doing to type out MIA while I am in the middle of a fight. It’s just plain stupid to do this. You will be opening yourself up to a world of hurt if you suddenly pause. And it might not have even been worth it because maybe they weren’t going to gank, just laying down a ward.
But knowing where your enemy is, is not just important for prevent ganks. It’s also important for pushing lanes, doing your own ganking, taking dragon and/or baron, and pretty much every other aspect of the game. If you know that 2 people went back to buy, and there is a 3v3 at your top turret, it’s fairly safe for you to push bottom or take dragon if you have the firepower.
Once out of the laning phase and on to mid or late game, MIAs become far less important, but much more deadly. If it is not your job to be by yourself (Master Yi and Twisted Fate, I am looking at you…) and you are out alone with no enemies visible on your mini-map, they ARE coming after you, and you WILL die. It is a good idea to discourage this kind of soloing on your team. If I see someone running around by themselves, way over extended pushing a lane, I will type ALL MIA to try and get their attention. And if it’s the enemy, group up and take them out. But again, you need to understand that the enemy team is missing and that tasty Veiger off by himself may very well be bait in a very big, very deadly, fishing net.