Anyone working in digital should take a moment to read the PDF from Society of digital agencies called Patent Infringement Risk - A Rising Challenge for Digital Agencies. Those worrying about Patent Trolls will find concrete steps on how to avoid stepping in it here.

Agencies, both in and outside the U.S., are often unaware of the significant infringement liability which results from meeting their clients’ needs. For example, a commonly requested feature for websites and mobile applications is one which presents a user with a list of nearby retail locations based on the user’s geographical location (as determined by IP address or GPS coordinates). While this may seem commonplace
and standard, advertising based on geographical proximity is currently the subject of a number of patent infringement lawsuits brought by GeoTag, Inc. (the now-infamous US Patent 5,930,474). Over 400 defendants have been named in the pending litigation, and the list continues to grow