16. The computer-readable storage medium of claim 13 , comprising instructions that when executed cause the system to: obtain a user context for a user of the client device displaying the video data; and use the user context to select an advertisement.
16. The computer-readable storage medium of claim 13 , comprising instructions that when executed cause the system to: obtain a user context for a user of the client device displaying the video data; and use the user context to select an advertisement. 17. The computer-readable storage medium of claim 16 , comprising instructions that when executed cause the system to: obtain the user context from at least one of: social network data from the user; user demographic data about the user; companion content on a web site displaying the video data; and browser history data.