1v1 on Summoners Rift

First, sorry if this is in the wrong section.

I was wondering what the general attitude is on going 1v1 during a game of 5v5, particularly in a ranked game. I am against it myself, as I feel it can very negatively impact the result of the game. I played a game recently were a member of my team wanted to 1v1 the enemies best player right before we made a push to win, and had he gone through with it and lost, we would have been royally screwed. I personally don't want to get a loss just so someone else can have a personal victory.