That... makes quite a bit of sense. We should get into a group and try that sometime.
I'm always curious, though... Why is mid the 'solo' lane for most groups? I mean, it's the fastest (i think) route. Why not send two or three there and the rest elsewhere? :/
Let me explain the whole concept:
The point the laning phase is to level up and get gold, so obviously the hero in the solo lane gets twice as much gold and exp than the other lanes.
Mid is usually solo because it's harder to gank
(it may have 2 entrances but the large space at the bush makes a huge difference!) and everyone would prefer to have the guy alone on a lane to be in a safer location instead of having 2 players in a safe location because they have advantage in numbers.
I don't know at what Skilllevel you play, but later you will see players start jungling, which means one player will kill the neutral mobs in the jungle instead of going on a sidelane. Again, this has the advantage that you now have 2 solo lanes, the jungling guy also gets a nice amount of gold and since the enemy team can't see where he is, he can also set up ganks easily.
Now pushing a tower early means that you cannot safely farm anymore, because the creeps will get pushed beyond the destroyed tower and then you're stuck in the enemy lane, where you can very easily get flanked from the jungle. Also, early on, pushing is much harder because you do less damage to creeps, so 2 players should be easily able to defend against 3 players by just sitting under the tower, widening the exp and gold gap while you're unable to push farther, unless you manage to kill them(which will probably reduce your hp by a lot) and even then the time spent dead is very short compared to the later phase.
Another random tip: If you really, really want to use 3 people to push, let them all take the bottom lane. The reason for this is simply that the dragon is located between top and mid and it will spawn earlier than Baron(which you can't kill until much later anyway unless you use some silly builds). The dragon is somewhat easy to kill with a team and it will provide your entire team with as much gold as you would get for killing 2 heroes(the whole amount is split between the 5 players).