errr this is not a problem..this is a normal, if this didnt happen.then u could have predict that the world is about to end...
Common Reasons why ppl would leave:-
- First blood
- deny potion
- AR, get crappy hero
- cant solo
- cant hold Aegis
- KS

so to keep the game going, be humble and avoid/allow those..
but doing so, might make u lose, so anyhow if no leaver, u lose, if u win, got leaver