Ajax star rating bar

[eluser]mindprojects[/eluser]
Hi! guys,i'm developing a star rating system and i was following this post...
I looked through many star rating solutions and i found that(tell me if i'm wrong)
the GDstarrating @http://www.gdstarrating.com/ is the most complete one.

Why i'm telling this?yesterday i took a look at the surce code and this is the stuff i discovered:

The system is based on cookies first of all..but not only,to se if a user has previously rated,or to avoid bots it checks(in order):

1- is a bot?
2-has a cookie with the ID of the article?
3-then it goes to the database and check:
3.1 - if the user is not legged it checks if someone else has voted for that ID from the same ID
3.2 - if the user is logged is checks if that user_id has voted for that ID,not checking the IP.

I have seen also that this syem is very appreciated all over the web!
From the othe side,i was thinking that this is not so god at first sight,why?

All right:
The system is good till the point 2,but we should mod the third one because:
1- as you told guys if i'm in an office many people have the same IP...and if one is going to rate,another one can't
2- what if i rate when i'm not logged and then i log....i can rate two times..so bad!

This is my solution:
1- you first extablish a number of days/hours within a user from the same IP cannot vote if he deleted the cookie,doing this you would not avoid people getteing that ip to rate in the next future,
2- the you should also check that if the user is logged if he has rated...

So the ip check and the user check should be done togeter,like this:

function check_vote($id,$ip,$user_id,$maxtime)
{
$this->db->select('*');
$this->db->from('ratings');

$where = array('id' => $id);
$this->db->where($where);

//ip check inside a date range
$valid_interval = time() - strtotime($maxtime);
$this->db->where("ip = '$ip' AND date_rate >= $valid_interval",NULL,FALSE);

//if logged user_id > 0
if($user_id > 0)
{
$where['user_id'] = $user_id;
$this->db->or_where($where);
}

return $query = $this->db->get();
}

What do you think about???