There seems to be a lot of attention being paid to Google's answer to the Facebook Platform called OpenSocial. I heard about it on Pmarca's blog, but there are a lot of details here, here, here and here.
I think this attention is truly deserved, because it really opens up the field for innovative widgets/apps which run on these platforms. The major Facebook Platform app developers are also participating, which portends well for the adoption. Stay tuned for more observations, as I feel this is an exciting new opportunity where there will be a lot of action in the future.