The Team Fortress 2 Blog announces plans for Team Fortress 2 scheduled maintenance on Tuesday, and while the teamplay shooter will still be playable while that's underway, certain features will be unavailable until it is complete. Here's word:

This coming Tuesday November 9th, 2010 the TF2 item system will be down for maintenance starting at 1pm PST and ending at approximately 2:30PST. We are significantly increasing the amount of database horsepower behind TF2 to accommodate all the recent additions to the system. During this maintenance the following TF2 features will be unavailable:

        > Backpacks
        > Crafting
        > Trading
        > The MannCo store
        > Loadouts

The game itself will continue to work. All players will have their default appearance and weapons.

To keep abreast of the status of this and future TF2 item maintenance, subscribe to this thread in the TF2 forum.

Note to developers using the TF2 Item Web API: As part of this maintenance all item IDs will change to eliminate negative IDs. We will be shifting all item IDs forward by 2100000. Depending on what data you store in your database, you may need to do the same.