despite the refactoring of the scurvy media pipeline architecture, trying to add large videos will result in an out of memory exception. This is because under the covers, they're using a MemoryStream ... so even though *I'm* not using a lot of memory ... they still are.
https://connect.microsoft.com/feedback/ViewFeedback.aspx?FeedbackID=323222&SiteID=226
I filed the above bug report ... and I admit even in that bug report that my pipeline could just avoid writing so much data :-P and I am planning on improving that ... as soon as I can figure out how to write and then set the data texture data using dxt1 compression.
But I figured I'd file the bug report anyways as there could be some other reason to write lots of data to .xnb