This is from another site-- http://www.mini2.com -- that also uses vBulletin. Obviously all of the values are alterable by the individual board-owner-- as a small example, in the below you can see your last 10 reputations, on FT you can only see your last 5. I assume some of the values could be radically different here-- but it feels like many of them are similar if not the same (but that's strictly a guess, obviously.)

How does Reputation work?

Many have asked how the reputation system works. Below you will find the guidelines used to determine how many 'points' of reputation are awarded or taken away by each user.

Register Date Factor
For every 182 number of days, users gain 1 point of reputation-altering power.

Post Count Factor
For every 500 number of posts, users gain 1 point of reputation-altering power.

Reputation Point Factor
For every 100 points of reputation, users gain 1 point of reputation-altering power.

[Administrators give or take 50 points of reputation unless their calculated reputation-altering power is greater]

Minimum Post Count
Q: How many posts must a user have before his reputation hits count on others?
A: 100

Minimum Reputation Count
Q: How much reputation must a user have before his reputation hits count on others?
A: 30

Daily Reputation Clicks Limit [Administrators are exempt]
Q: How many reputation clicks can a user give over each 24 hour period?
A: 10

Reputation User Spread [Administrators are exempt]
Q: How many different users must you give reputation to before you can hit the same person again?
A: 20

Any user can let you know whether they approve or disapprove of one of your posts by clicking the [scales] button associated with the post. They should also provide a short comment as to why they approved or disapproved.

If you look in your User Control Panel you can see the last 10 reputations given to you. There will be a little dot next to each reputation:
• A green dot means the user approved of your post, and as a result your reputation has grown,
• A red dot means the user disapproved of your post, and as a result your reputation has "taken a hit",
• A grey dot means the user giving you reputation has not yet met the minimum qualifications to do so, and you will have to read the associated comment to determine what they thought.