We do not have a special key hidden, 
It has to be added to your config.php! Example:
// Your Akismet Key. You do not need a key to run bbPress, but if you want to take advantage
// of Akismet's powerful spam blocking, you'll need one. You can get an Akismet key at
// http://wordpress.com/api-keys/
$bb->akismet_key = ''; // Example: '0123456789ab'
Still requires getting a key from wordpress.com to work!
With the recent re-works of the admin, this might be a great option to store in the database through a core plugin!
Trent
Why not put an hidden special key in it? We all hate spam, now we have to sign up to get a key, edit the config file etc etc…
I say, put in a special bbpress askimetkey in it so we dont have to bother about spam 
Without stepping out too far on a limb, I think that each blog (or forum) has it’s own key to keep track of what is done with each user and require their own key. Since they are free, it isn’t too hard to get one, just go to this post and follow the directions.
I see what you mean about having a special bbPress key, but I doubt if it will ever happen in the near future.
Trent
The use of separate keys is important for several reasons, firstly, you’re not just using the Akismet database, you’re contributing to it with every message you send. Each time Akismet makes an assessment and you don’t disagree with that assessment, you’re contributing. Being able to remove contributions from bad people once they’re identified is a useful ability, if everyone used the same key this would be more difficult.
Obviously bad people very much want to be able to affect the DB so that their spam can get through.
So when bad people are spotted, they must be stopped. The key helps here too because (I recall from looking at the original plugin source) it becomes part of the connection URL, so it’s possible if necessary, to block connections to that URL at the firewall level, so the servers can concentrate on fulfilling requests from good guys.
A single hidden key would be very quickly compromised, and would thus be very quickly disabled, and you’d be back to needing your own key.
Nice! I learned something from that post! Wow!
Trent
Ahh ok, then I suggest to make things simpeler, perhaps on bbpress install:
ask the user to enter his/her askimetkey with an option to request a key if not heaving one
and/or
add an area in the admin where you can change/enter a key
Or should I make a trac about this suggestion?
Put it in TRAC as a recommendation. With the new options, this should be pretty easy to implement!
Trent
