If you're looking for one less thing to clutter up your Gmail space, GTalk can be one of your bigger offenders if you're using it to communicate often with friends or colleagues. Just taking a look at my own personal Gmail account, I'm kind of shocked how many threads there are for conversations I've had in the past year. On my work account I like to keep logs in case I need to reference instructions, facts, or quotes from people I've talked to. However, on my personal account I don't need to keep track of everyday chitchat.
That being said, I've decided to stop keeping the logs for my personal account completely, and here's how you can do it too:
Note: These steps will not prevent others from recording your conversations, that is only possible by "Going off the record" in each conversation.
For GTalk via Gmail on the Web:
Step 1: Log in to your Gmail account in a Web browser, then go to the Settings area from the cog menu in the top right-hand corner.
Step 2: Click on the Chat link along the top of the Settings area.
Step 3: Next to My chat history, click the bubble next to Never save chat history.
For the GTalk desktop client:
Step 1: Click the Settings link at the top of your Friends list.
Step 2: Open Chat from the left pane of the Settings area.
Step 3: Fill in the bubble next to Don't save chat history in my Gmail account.
Now you can reduce your Gmail storage clutter by having one less thing auto-save to your account.