Let google index the stream but make it visible to registered only - possible?

I know this is probably not possible though I hope that there is a way I did not thought of yet. There are so many using my stream but not using the forums or the blog. So all my content is on the stream and worthless for google indexing.

Is there any way to make it for registered only and having it indexed by google? I want to eat the cake and sell it at the same time.