Yes, it's based on helpful (5) and correct answer (10).
Why, the forums and communities are bor on the Internet to discuss and help some people which are organized by "idea". (sorry if this is not a good english sentence ) There are not born to be on top.
The user who post the orginal question can attribute correct or helpful to the relies in his thread.
I think maybe it will be also good to give some points for contributions when there are good contributions. For example, the Advanced Admin Tool I have uploaded is now the #1 in the popular downloads and has also been rated, but no points for me. :P
If you don't want to attribute points for a question you have, you can deselect the option that tell this is a question.
Each Forum is also assigned a Subject Matter Expert as a moderator. Moderators can't grant or remove points but we can make notations/edits to the post that was granted the points to correct or clarify if an answer is deemed incorrect. If you see a post with incorrect info, add a correcting (in your opinion) reply. This will definately cause the moderator to review the thread.
Moderators also have the ability to move threads that are posted in the wrong forum to assure that the appropriate audience is looking at you question and may provide an answer. Although, we hope with time, you will all get used to posting in the appropriate locations