1. An automated method for dynamically generating and serving advertisements in the form of composite video clips by a computer, the method comprising: providing a template advertisement including at least one video clip and a plurality of placeholders for the use of video players or widgets to be replaced with content at run-time, each said placeholder being associated with a respective rule; and at run time for each of a plurality of recipients producing an individually targeted advertisement comprising an instantiation of said template advertisement by: for a given recipient of the plurality of recipients, automatically parsing one or more data sources other than the template advertisement for one or more data items corresponding to the placeholders, the one or more data sources being selected from web pages, RSS feeds, files, web services and databases; automatically extracting from the one or more data sources the one or more data items, wherein each of the one or more data items has a data component type corresponding to a placeholder component type associated with a respective corresponding placeholder; automatically replacing said placeholders with the one or more data items based on said respective rules; automatically generating an individually targeted advertisement for the given recipient in the form of a composite video clip including said video clip and said one or more data items, wherein for each placeholder, said respective rule describes an arrangement of the respective data item over the video clip; and serving the individually targeted advertisement to the given recipient; wherein the one or more data sources contain dynamic data and different instantiations of the template advertisement contain different data items depending on the target recipient.