Wes Blemker on Branding and Search from the ROI point of view:
The most common argument against bidding on your brand is that it costs the company unnecessary marketing dollars. If the site is already showing up for “free” at the top of the organic results for a brand search, then what is the point of paying for a click? Well, in addition to the clear benefits of having your brand appear as many times as possible on the page (as Lance discussed above), it is also usually justified to do it from a pure ROI perspective. By losing these highly targeted brand clicks to your competitors’ sites, you are not only increasing their revenue, but you are missing out on (often times) the most highly converting traffic you could get. Being the official site of the brand search makes it easier to have an extremely high click through rate on your brand ads, and, hence, pay a much lower CPC than your competitors to remain at the top of the paid search results. In most cases, we have found that this low cost of bidding on your brand clearly outweighs the loss of highly qualified traffic (revenue) to competitor sites.