How is Google going to respond to it? Should we expect BigTable opensourced any time soon?
Their solutions may be optimal for Facebook, and they may even be generally useful to folks building large scale websites. But, their Open Source tools are no threat to Google, and would have no impact on Google's decisions about what to Open Source.
Hadoop/HBase has already been offering BigTable like capabilities in an Open Source project. This is merely another option--and frankly, one that sounds a bit half-baked at the moment. But I could be wrong about that. And, of course, Thrift is yet another RPC system. It makes pretty bold claims about being uniquely lightweight and cross-language, but the RPC and data interchange problem has been solved many times in the past in many ways. I don't think the world has been set on fire by Thrift.
For example JS-Kit.com generates 10G-100G worth of data a day. They had to create an equivalent of Amazon's Dynamo to handle it. Easily half of their resources are dedicated to maintaining and extending this infrastructure. Now imagine if they could just use Cassandra and focus on their core? I do not know what Disqus or FriendFeed are using (probably mysql?), but they can benefit from it too once they grow.
That could affect Google too, there will be more competition from smaller startups like webmynd or cuil because of it. And if startups adopt Facebook's tools instead of Google's, that would make them less attractive to Google as an acquisition target.