About leaving dota games

[lolocaust]

Recently ive seen some people leave mid game and still see them able to join other ent dota games.
Also been in many games where my team leave mid/late game which is kinda boring because it happens quite often.
Probably they know when its right time to leave so they dont lose elo/ban (which is kinda stupid,who cares)
Now if someone could explain me when i can leave game if its 2v5 or 3v5 without getting a ban,because its seriously pointless to play.My team gets raped or vice versa.
cheers

[uakf.b]

You can leave when there are less than four players on either team.

[lolocaust]

cheers.