The biggest danger of trying unconventional champion placements is that the rest of your team with sometimes just give up in champ select.

Like just recently I played a game were our support wanted to play as victor. I thought this was strange but ok, but out ADC tristana just totally gave up and started building tiamat.

Despite this we managed to gain a 10-5 kill advantage over the enemy team but our trist continued to whine and moan about her lack of support. Eventually we lost as the enemy team had alistar and singed and eventually became too tanky to kill as trist was our only damage aside from fizz.