well, the people that play on a regular basis would then have a say in what maps should be on a given server, and if set up correctly it wouldnt take hardly any time.
abuse is something that is for the most part unavoidable. but you might be able to reduce it by limiting the amount of voting in a given amount of time. another possibility would to vote on clan sites. this would limit the abuse and encourage new players to get involved with a clan. or with the global login system, where only clan members can vote, or their votes are worth more.