Web polls are a great way to engage with your visitors on a simple issue and get their feedback/support. Generally only a small percentage of the visitors to a web site will do anything that requires their input, however with the right question polls can be very effective. Where they have failed however is that too many polls have been hacked by users who want to unduly influence the results. Historically there have been three main ways to ensure that web polls aren't hacked by people trying to influence a decision online.

The simplest one was to just store a cookie on in your web browser so that the script knew that you had already voted. Unfortunately, this was super easy to hack and just required someone deleting that cookie and voting again. Some people have a great deal of time on their hands it seems.

The second allowed tracked the IP addresses that users had when they accessed the net. This was faulty because often an organization will share a single IP address. Users could also vote multiple times simply by connecting to the net from a new location.

The better solution is to tie a vote to an email address. Some popular polls require you submit your email address in order to track participation and watch for spoilers. Many organizations like this method because it is an easy way to gather email addresses of people who frequent their sites. Unfortunately, many people now have several email addresses so this isn't a perfect solution either.

Because of Drupal's flexible permissions system it is possible to create a system which avoids many of the problems of the above solutions. Thanks to the flexible access control you can set roles for users, and assign who can cancel their own vote, create new polls, inspect all votes and vote on polls. You can restrict the rights of anonymous visitors so that only people who have registered for the site can vote. This can be set up so that anyone with an email address can easily do so. Registration is simple enough that it doesn't take that much more time for users to do it. However, the real strength is that thanks to the CAPTCHA module, it can be made nearly impossible an automated bot to fix the votes.