i said null.. only because it depends for what kind of poll you are doing...
i didn't want to say no because i do somewhat like the idea.
although if you did that in this forum, it would defeat the purpose (1st post someone said already) of the favorite choice such as no...
if they can do that some people may pick both no and yes and take more time for a lot of people to vote and change site or w/e

also in polls that someone is actually wanting info from such as "should i get a name change) it may get abused because people will always choose more than 1 name that they should get.
p.s. i do realize some of that might of made no sense.. but i know what i'm talking about so i hope you catch the drift

i think we could always add this because if someone want's this they can set more vote's.. but can also keep it on 1..