On March 18, 2011, ICANN approved ICM Registry’s .XXX top-level domain (TLD). To hedge against an obvious public relations nightmare (think http://www.[yourbrand].xxx) and future infringement, you can take preventative action through ICM Registry’s Sunrise Period.
Businesses can purchase keyword-triggered advertisements through online ad networks, such as Google, well known for its AdSense program. Through AdSense, purchasing a keyword results in your ad being shown when a user searches for that keyword.