>"Public cloud bandwidth is obscenely priced compared to what you can get it for on the CDN market"
Amen to that! I think where this comes in to play is when you've already got colo space and excess capacity (e.g. eBay etc) and/or you'd like to leverage other edge pop's outside of your provider (e.g. mainland China). But it also adds some level or protection against correlated backbone issues if you can add p2p edges along other providers (similar to Netflix's design). When we looked at the correlation across existing CDN providers we found it was ~95%.
Video streaming specifically is _especially_ bandwidth intensive and will definitely cause issues in corporate LANs. It's one of the reasons we add ASN categorized black listing (e.g. residential vs. hosting vs. corporate etc)