Now, understand, the tool is free, but multivariate testing still costs you time and effort that you'd be spending on other things. You must take the time to develop multiple versions of your content and you must load up the page with some JavaScript and run and monitor the experiment. You can check out Google's multivariate testing instructions to gauge the effort required.

The effort is worth it. At last October's Emetrics Summit, Regis Hadiaris, the Director of Web Marketing for Quicken Loans, said that the use of multivariate testing has increased revenue 30 percent per year every year. ReallyGreatRate's case study is also persuasive. You ought to be testing variations to improve your site anyway—multivariate testing is just a better way to do it.

Just as when Google began offering a free Web traffic metrics service, Google Analytics, some folks have questioned whether marketers should allow Google access to this highly-valuable marketing information. Andrew Goodman, in particular, has written persuasively about this "fox in the hen house" situation where a company you buy advertising with knows how much you sell and what it is about your site that sells it.

For small businesses, "free" is more important than data privacy, but larger marketers might be better off using Optimost or another licensed multivariate tool that protects the privacy of their testing data, just as they might use CoreMetrics or another fee-based analytics tool to protect traffic and conversion data.

Regardless of the data sharing issues, your company ought to be using multivariate testing to optimize your customer conversions. And if the cost of a licensed tool seemed too formidable before, now you have no excuse. Google Website Optimizer makes that free.