Validating Users in Poll Voting Etc.
 

Have any of you come up with a creative way to validate users when setting up & voting a poll? The organization I belong to would like to be able to vote on things via the vBulletin board because of everyone is geographically spread out but would like a way to verify people are who they say they are. I can set up a forum that requires an additional login but would like to take it one step further if possible. Any creative ideas out there? Is there any way to identify each voter or user's post origin so people aren't voting multiple times etc.?