UPDATE: apparently this only happens when fetching videos from a playlist feed, which is what I'm doing.
I recently noticed my youtube api requests for videos were returning blank keyword entries. I found the blog post at http://apiblog.youtube.com/2012/08/video-tags-just-for-uploaders.html, and I'm already sending requests as the channel/video owner, yet I still get blank keywords. This has the undesirable side-effect of deleting existing keywords if I make any changes to the video details, such as to descriptions or titles.
For instance, I have video series where every video will have the same description. Perfect place to use the API to run through all the vids in a list and update their details. This used to work fine. But one ill-fated day, this routine became destructive. Any time I do this now, the keywords get blanked out, and I have to go back through all of the affected vids, replacing the lost keywords by hand. I've stopped using my API-based utility since this began happening.
The descriptions and titles will get updated as desired, but the keywords get blanked out, even if I don't touch them. I recall reading somewhere in the API docs something to the effect that when you submit updates for video details, any entries not filled in will be erased. In this instance, because the keyword entries I get back are already blank, any updates I do to the video other than to the keywords cause the keywords to be deleted.
Anybody have any ideas or workarounds? If I can't continue using the API to manage keywords, I would at least like to be able to continue making updates to titles and descriptions, but that won't work right now because the keywords get deleted with any title or description updates :(