Whenever you want to run Selenium against a site, please understand it will trigger all the javascript and act like a fully functional browser, it will trigger all kinds of services that might impact target website.

For example, while I was playing around with Selenium this morning to hit against my own website. It actually totally mess up the monitoring tool comes with wordpress and now, my poor traffic has been heavily skewed by the traffic that caused by Selenium. In another way, if you did this to some business, there google analytics might be totally screwed and it is not beneficial to any one.