>> Gbps is -as far as I know- for private use is still very much a concept with just early prototypes available.
We've had 1000Mbps FTTH / FTTOffice for a while here in HK and other parts of Asia. ( 2006 in Hong Kong - [hkbn.net...] )
Causes very unique load balancing and throttling problems on servers hosted locally if you get a swarm of high speed users get on your server.
Since YouTube and other critical Google datacenters are all in the US, they do not see the effects of these users hitting their servers (global connections get severely throttled...).
I can see why they need a test lab of 50-500K users on 1Gbps links - specially for apps like YouTube, Maps and the rest of their ajaxy application infrastructure.