http://forums.steampowered.com/forums/showpost.php?p=28255326&postcount=199

Today the Team Fortress team took action to bring certain server operators into compliance with our previously announced "honest server policy". Examples of server modifications that resulted in this policy include:
* Running bots and trying to make them appear that they were human players
* Running bots and circumventing or modifying the usual mechanisms that the bots are advertised to the server browser
* Running with significant gameplay modifications, such as respawn times, without having the proper tags on their server designed to alert quickplay and automated searches about those modifications.

We have not taken action against individual servers, but rather against an entire related server group. Hopefully the necessity for this policy is clear. We took two different actions, depending on the severity of modification we found:
* Preventing IP addresses from logging a TF gameserver account, which excludes them from quickplay.
* Delisting IP addresses from the master server (server browser and Quick Match system) for one month.

Finally, we would like to say thanks to the server operators who have continued to run honest servers, and to those who heeded our earlier warning and subsequently changed their practices. We thank you for that. We hope that our actions today show that we want to help you compete for player traffic on the basis of providing a good environment for players.

Thank you,
The Team Fortress Team