As announced over at Google's Inside Ad Words blog, they have just turned on daypart scheduling and now you should too. Google will now let you schedule when your ads will run or more importantly when they won't run. This is really big news especially if your business is skewed to a certain time of day or day of week.
In the brokerage and financial services world this means you want to shut off or turn your bids down to a minimum on weekends; personally, I'd shut it off altogether on Saturday and Sunday and then put about 70% of my bid dollars between 7AM and 7PM on Monday-Friday. Other businesses will have to decide what works best for them, but remember that the internet if very popular during the work day (you didn't really think your employees were looking for competitive data).
I'm not sure how we should place our political ad bids, but the first thing I'll look at is the normal site traffic to understand the distribution. I'm sure there is a pattern in there.
MSN already allows dayparting and Yahoo will add it in later this year. So, start keeping an eye on your traffic and bids during the day, because it is already impacting your business and now you can match it with your Google campaigns. And, if you are in the financial services industry, trust me and use the strategy I outlined above; it comes from buying millions of dollars worth of search in this industry since almost the very beginning.