In Tiki 10 (trunk at time of writing, 2012 August) a new feature has been integrated into forums called "Deliberation" in an early experimental state.
Note:
Keep in mind that basic deliberation can be achieved already in Tiki12 in forums when you enable the more stable features Ratings per forum and Ratings in comments. See Rating for more information.
According to Wikipedia:
Deliberation is a process of thoughtfully weighing options, usually prior to voting.
In other words, a deliberation (in Tiki) is basically a rating system where a single forum topic has multiple opinions, where each can be rated on a scale.
Why is this different than a rating or a vote?
Rating:
Gives you a single "opinion" to rate
Vote:
A single vote, generally yes or no
Deliberation:
Rate multiple choices rather than a single choice.
Rate on a scale
More than a single opinion that can be rated
Example in forums
The forum post, after it has been weighted through the deliberation feature by a couple of users, looks like this for a plain regitered user that has just rated the two opinions:
Click to expand
And this is how the same post would look like for the admin of that forum, in which some visual display of all the ratings for that post is shown with colors: