The SPListItem being updated was not retrieved with all taxonomy fields

Turns out it’s a central admin setting that throttles the lookup return count, and Taxonomy fields are just lookups under the hood.

Go into Central Administration –> Manage Web Applications, select your web application, and then in the ribbon choose the dropdown under General Settings select Resource Throttling. Find the setting for “List View Lookup Threshold” and raise it from the default 8 (can go up to 1000, but 20 is likely fine depending how many lookup fields you’re pulling back in your SPListItem).

Streaming and buffering in SharePoint 2010

The best single link is a fairly new Technet article on caching and performance planning with SharePoint 2010: Summary: performance can be tuned through disk-based BLOB caching and bit rate throttling

Bitrate throttling configuration walkthrough: Summary: detailed guide from the IIS team

More direction on where we’re going with streaming (the out-of the-box media web part uses buffering, NOT streaming. Streaming is enabled via IIS media services): Summary: good overview of IIS Media Services 3.0

And finally, Silverlight 4 capabilities, including multicasting. Currently SL4 is in beta: