How often do we hear about $50 million in paid search, millions in TV or tons of money in some other acquisition tactic?
Not enough attention (or funding) is paid to website optimization. You can spend all the money in the world to find and get people to your website, but if you aren't spending against optimizing and improving your site's performance, you're throwing your $ away.
Great tools like Omniture's Test and Target, Google Site Optimizer exist just to help your site convert better. All offer A/B and multi-variate testing capability that will really help you drive the most benefit from those millions you're spending in acquisition.
So, are you spending the way you should be?